1

The Removal of Superficial Rust/Corrosion From the Working Surfaces

of Firearms For the Purpose of Revealing Their Potentially Identifiable

Signature and an Application of this Technique in a Firearms

Identification By: Philip A. Hess, BS, MS and Bruce Moran, BS; Sacramento County District Attorneys Laboratory of

Forensic Services, Sacramento, CA

Key Words: Corrosion, Hydrofluoric acid, IBIS, Oxidation, Pitting, Rust, Rust Removal, Whink,

Working surface.

Abstract: A method for removing superficial rust and corrosion from the working surfaces of

firearms with the intent to restore any potentially surviving identifiable signature of the firearm is

discussed. The method involves the use of a chemical with an active ingredient, hydrofluoric acid, to

solubilize superficial rust adhering to the working surfaces. The benefit of this method is the

restoration of the working surfaces of firearms that otherwise would not be suitable for the

preparation of exemplars for comparison. The results demonstrate that the method, when applied

appropriately, is successful. A case resulting in the identification of several bullets to a rusted

firearm treated using the procedure described is also presented.

Introduction

Periodically, firearms examiners and Integrated Ballistics Imaging System (IBIS) technicians receive

requests to examine firearms that have been oxidized (rusted) and/or corroded due to a variety of factors.

In many cases the areas of greatest interest are affected by this rust/corrosion, these include the breechface

or bolt area, firing pin and firing pin aperture, ejector and extractor, chambering area, barrel, bore, etc. This

rust/corrosion makes it difficult for the IBIS technician/firearms examiner to test fire the firearm and obtain

reliable exemplars of bullets and cartridge cases for entry into the IBIS database. Additionally, any test

firing conducted while the firearm is in this condition risks permanent alteration of the weapon’s signature

on these working surfaces for purposes of IBIS entry and future identification/comparison. Consequently,

any steps taken to prepare the firearm to be test fired successfully must be done with the consideration that

the exemplars must be of comparison quality, should a correlation to fired components from another

criminal case be determined at a later date.

Corroded or rusted firearms may be handled in various ways when encountered in casework. For example,

the IBIS technician/firearms examiner may simply choose not to test fire the firearm at all, preventing

potentially valuable information from being correlated against the images in the database. Given the

2

backlog that most agencies are facing in this time of budget restraints, increasing caseloads, and

understaffing in firearms units across the country, the probability that firearms received in corroded

condition will not be test fired at all is likely. Without test firing the firearm, the potential to link any

previous entries already in the IBIS database where that firearm may have been used in the commission of

a crime, would be a missed opportunity for the examiner to provide investigative leads for submitting

agencies. In some instances, rust and corrosion may be superficial and consist only of visible discoloration

and superficial rust adhering to the working surfaces of the metal, with little permanent damage. This is a

likely possibility when encountering firearms with stainless steel surfaces.

In other instances, a non firearms examiner or IBIS technician may choose to test fire the firearm in its

corroded condition, with the belief that attempting to remove the corrosion and prepare proper

photographic and written documentation would be too time consuming. If the firearm is test fired in such

condition, the action of the bullets passing through the barrel will pick up the corroded materials and carry

them down the bore, likely causing permanent scoring which adversely affects the signature of the barrel in

question. Likewise, firing the firearm in a corroded condition without treatment could cause significant

changes to the signatures of the working surfaces associated with the cycle of fire such as the breech or bolt

areas, firing pin, ejector, extractor, magazine feed ramp, chamber area, etc. Consequently, test fired

components entered into the IBIS database will be devoid of useful information for comparison, as the

“exemplar” bullet would exhibit a different signature than any bullets fired previous to the presence of

corrosion. The information contained on the test fired bullets would, therefore, be different than that of any

previously fired bullets from potentially criminal related incidents. Subsequently, such exemplars would

most likely go undetected by the IBIS correlation software as being fired from the same firearm. Most

importantly, the information contained in that barrel may be permanently changed, making it more difficult,

if not impossible, to identify/associate it to any bullets previously fired through that barrel.

Some IBIS technicians/firearms examiners may attempt to remove rust/corrosion deposits by passing

materials through the barrel such as a dry patch or other cloth materials, a nylon or even a metal brush.

Such methods increase the risk of changing the barrel bore signature through the same abrasive actions as

previously described when a test fired bullet passes through an untreated corroded barrel. Without

attempting to loosen/solubilize the rust with a non-abrasive solvent before passing a nylon brush or dry

patch through the barrel of the firearm, the risk of permanently changing the signature of the firearm is

potentially greater.

Search of the literature for a minimally destructive method to remove rust/corrosion:

A review of literature published in the AFTE journal revealed several articles that addressed some of the

issues concerning firearms that were received in a rusted/corroded condition. The main focus of these

3

articles, however, were concerned with the issue of making a firearm that is inoperable due to

rust/corrosion issues, operable. The articles did not address the issues involving the potential for damage to

the identifiable signature of the firearms working surfaces as a result of the treatment processes described

in the articles.

In the article Making A Rusted Gun Functional, the author used a product called Break Free CLP which is

commercially marketed to Clean Lubricate and Protect (CLP) metal. 1 This product is not marketed as a

rust removal chemical, but rather as a lubricant that reduces the adhesion of sand, grit and abrasives. It also

prevents moisture and contaminants on firearm components. 2 The author went on to credit the

preservation of the rifling and ultimately the ability to identify a test fired bullet to the fatal bullets to the

“fact that the pistol was equipped with a silencer and there was a cartridge in the chamber.” 3

Another article that addresses the issue of making a firearm operable, that is inoperable due to

rust/corrosion issues, suggests a cleaning procedure that begins with “brushing or picking off loose deposits

of dirt and rust. Wire brushes, picks, knives and files may be used to cut thru and remove large deposits.” 4

While the procedure mentioned in this article may be successful in making a firearm, which is received in

an inoperable condition operable, the affects this process would have on the signature of that firearm would

be detrimental.

One article specifically discusses the issue of receiving firearms with rusted barrels and other components.

It addresses concerns regarding rusted barrels and test firing: “If a bullet recovered from a crime scene is to

be compared to a bullet fired through the barrel of a weapon that has been in water or damp soil it is logical

to assume that the rust should be removed from the barrel prior to test firing.” 5 The article discusses

numerous industrial cleaning and descaling processes including acid pickling. Pickling is a process of

removing contaminants such as ferrous and ferric oxide particles through the use of nitric (HNO3) and/or

hydrofluoric (HF) acids to remove the scale and restore corrosion resistance. The author described acid

pickling as not being a suitable method for laboratory use because, “(a) the acid temperatures of 130°F

require special safety precautions, (b) careful monitoring must be maintained to avoid removal of the base

metal, and (c) this procedure is most useful when the depth of rust is generally uniform over all exposed

surfaces of the object.” 6 The authors of this paper took each of these concerns into consideration and

developed a less aggressive procedure based on the principles of this industrial corrosion removal

technique, which will be described in the following section.

Two articles that discussed rust/corrosion with respect to firearms did not specifically address concerns

regarding the treatment and removal of rust/corrosion with respect to the effects on the signature of a

firearm. One article addressed the issue of how long a firearm could be submerged in salt water and/or

fresh water before the exposure to these conditions affected the potential to identify ammunition

4

components test fired from them.7 The article discussed the effects of corrosion on the potential to identify

test fired bullets fired from rusted/corroded firearms, but did not discuss any method of treatment to remove

the rust/corrosion before test firing the firearms.

The other article was a case report where a .38 caliber revolver was found after being cemented in a

concrete slab for an estimated forty years. The firearm was extensively rusted and all of the working parts

were seized by the corrosion. In this article, the firearm was left for an undetermined amount of time in a

solution of “Penetreen, a liquid recommended for the freeing and lubrication of rusted parts.”8 After

treatment, the firearm was test fired into a water recovery tank and the recovered bullet was found to be

devoid of all rifling. “All rifling in the revolver’s barrel was destroyed by rust of course and the view down

the bore wasn’t pretty – it was dull and rough, the surface extremely pitted.” 9 The author indicated that

identification was never the goal of the treatment process, “this restoration was not carried out with a view

of obtaining test cases and bullets for comparison with unsolved crime exhibits. Quite obviously the

individual characteristics and most of the class characteristics had been destroyed decades ago. Rather this

exercise was conducted to see if the weapon could be restored to a condition where it could be fired,

despite its apparently useless condition.” 10

The method described in this paper was developed with the goal of removing rust/corrosion from the

working surfaces of a firearm while minimizing the potential for changes in the signature of these surfaces

as an alternative to the more mechanical removal approaches previously discussed. The chemical used in

the process described in this paper is Whink Rust Stain Remover [active ingredient Hydrogen Fluoride

(2.5% – 3.0%)]. This chemical is marketed for household use in the removal of rust stains from white sinks,

white toilet bowls as well as colorfast fabrics and carpets11. The action of the Whink Rust Stain Remover

is most similar to that of pickling. The following process described is conducted under much milder

conditions than standard pickling, in that: 1) the chemical process is conducted at room temperature and

not at the suggested 130°F of standard pickling; 2) the solution of hydrofluoric acid is very dilute

(approximately 2.5 to 3.0%); 3) the solution is gently agitated with cotton tipped swabs; 4) and the process

is strictly monitored through the use of the stereo microscope and/or bore scope and is subjected to the

action of the chemical for a minimal amount of time (generally one to three minutes is sufficient to just

remove the superficial corrosion deposits).

The authors acknowledge that this method contains certain inherent risks and should be employed when the

condition of the firearms working surfaces dictate that all other viable options are inadequate and there is

“nothing to lose” by attempting to preserve a firearms signature by applying a selective but none-the-less

potentially destructive method for removal of rust/corrosion. The authors note that with regard to the

referenced articles, the firearms were, seemingly, received in such poor condition that this treatment

process, and most likely any treatment process would not have been sufficient to salvage the characteristics

necessary to associate the firearms to any questioned fired components. The following procedure describes

5

a method for addressing superficial to minor rusting of the working surfaces of firearms and is not meant as

a method for “restoring” permanent damage to the working surfaces caused by rust/corrosion. This

procedure merely describes a method for: 1) removing superficial rust adhering to the working surfaces

and thereby revealing any remaining signature and; 2) to prevent any further change to that signature,

which could be caused by test firing the firearm in an untreated condition.

Suggested Method For Removing Superficial Rust:

Recommended Supplies:

• Stereo Microscope

• Bore Scope

• Rubber Stopper or Cork

• Pasture Pipette [glass or Nalgene plastic]

• Whink Rust Stain Remover

• Sterile Swab (Cotton) and/or Nylon Brush

• Distilled Water

• Acetone (CH2COCH3) and/or Methanol (CH 3OH)

Visual Inspection/Pre-Treatment Documentation:

1. Using a stereo microscope, visually inspect the breech/bolt area, chamber and bore for rust,

corrosion and/or debris that may require removal before the firearm can be test fired.

2. Using a bore scope, visually inspect the inside surface of the barrel bore and chamber to look for

rust and corrosion, noting any potential pitting or other permanent damage.

3. Photograph and describe the condition of each area of the firearm to document the condition in

which the firearm was received. Remove the slide and barrel (if applicable) and photograph those

areas that will be treated: breechface, firing pin, ejector, extractor, chamber, bore and as much of

the interior barrel as possible.

4. Whenever possible, prepare a Mikrosil cast of the interior of the barrel bore and chamber to

permanently record the surface conditions prior to corrosion removal treatment. Examine the

Mikrosil casting of the bore for the distribution of rust deposits and document any “clear

channels” of rifling that may be either unaffected or minimally affected by rust. Such pre-

6

treatment casts can be compared to post-treatment casts to critically evaluate the extent of surface

change.

Application of Whink Rust Stain Remover to the Breech, Firing Pin, Extractor and Ejector areas:

1. After properly documenting the working surfaces of the firearm, apply Whink Rust Stain

Remover to the breechface, firing pin, ejector and extractor using a pasture pipette.

2. Observe the action of the chemical under a stereo microscope. Gently apply a cotton swab to the

rusted and corroded areas, carefully absorbing the chemical and solubilized rust. Repeat

application and swabbing as needed.

3. Note the conditions of the treatment in your notes, i.e.: number of treatments, time chemical was

applied during each treatment and manner of application. After an appropriate amount of

immersion in Whink Rust Stain Remover, lightly agitate the areas with a cotton tip swab or nylon

brush if needed. A stereo microscope can be used to closely monitor the progress of the corrosion

removal.

4. Repeat these steps for short periods of time and examine the treated areas for progress until a point

is reached when the rust/corrosion deposits are completely removed. At the moment this occurs,

immediately cease further treatment to minimize any change in the non-corroded areas.

5. Immediately rinse the surfaces with a liberal amount of distilled water to adequately wash the

Whink Rust Stain Remover off the treated surface to prevent further chemical action.

6. After the areas have been completely washed with distilled water, rinse the surfaces with acetone

to remove the water.

7. Once the acetone has evaporated, apply a lubricant such as Hoppe’s or 3-In-One lubricating oil to

help prevent the return of rust.

Application of Whink Rust Stain Remover to the barrel/bore area:

1. It is necessary to create a leak proof seal in the chamber area of the barrel to allow the Whink Rust

Stain Remover to reside in the barrel for a controlled period of time. A cork or rubber stopper

may be inserted into the chamber area to create a tight seal to retain the liquid.

7

2. Using a pasture pipette, dispense enough Whink Rust Stain Remover into the bore to fill it

completely.

3. Gently apply a cotton swab to the rusted and corroded areas, carefully loosening the solubilized

rust.

4. Note the conditions of the treatment in your notes, i.e.: number of treatments, time chemical was

applied during each treatment and manner of application. After an appropriate amount of

immersion in Whink Rust Stain Remover, lightly agitate the areas with a cotton tip swab or nylon

brush if needed. A stereo microscope can be used to closely monitor the progress of the corrosion

removal. A bore scope can be used between treatments to observe corrosion removal progress

between applications of the Whink Rust Stain Remover.

5. Repeat these steps for short periods of time and examine the treated areas for progress until a point

is reached when the rust/corrosion deposits are completely removed. At the moment this occurs,

immediately cease further treatment to minimize any change in the non-corroded areas.

6. Once the rust/corrosion has been removed, immediately rinse the surfaces with a liberal amount of

distilled water to adequately wash the Whink Rust Stain Remover off the treated surface to

prevent further chemical action.

7. After the interior of the barrel has been completely washed with distilled water, rinse the barrel

surfaces with acetone to remove the water.

8. Once the acetone has evaporated, apply a lubricant such as Hoppe’s or 3-In-One lubricating oil to

help prevent the return of rust.

9. Pass a dry patch through the barrel to remove any excess oil from the barrel.

10. Prepare a Mikrosil cast after the treatment process. This cast can be compared to the casting of the

bore made before the treatment process. This will most accurately document the condition of the

bore both before and after the treatment process.

Visual Inspection/Post Treatment Documentation:

8

1. Note the extent of any permanent pitting on the working surfaces in the barrel, chamber, and

forcing cone areas as well as in the breechface, firing pin, ejector and extractor likely to have been

caused by the corrosion, by direct examination with a stereo microscope and bore scope and by

comparing the pre and post-treatment Mikrosil casts of the barrel bore.

2. Note the presence of any surviving manufacturing caused machine tool contours.

3. Re-photograph all of the areas that were previously photographed prior to treatment to document

the condition of the firearm after the treatment.

Test Firing

It is recommended that the firearm be test fired as soon as possible after the above procedure is completed.

This is to minimize the chance of continued degradation of the working surfaces in the event that residual

amounts of the active ingredient in the Whink Rust Stain Remover (hydrofluoric acid) is not completely

removed from the firearm. IBIS CASE DESCRIPTIONS AND PHOTOS

Case #1: This Makarov brand, 9x18mm Makarov caliber pistol was received in rusted/corroded condition to be test fired and entered into IBIS.

Makarov breechface and firing pin before Makarov breechface and firing pin after treatment treatment

Makarov barrel bore before treatment Makarov barrel bore after treatment

9

Makarov chamber area before treatment Makarov chamber area after treatment Case #2: This Jennings brand, model 48, .380 Auto caliber pistol, was received in rusted/corroded condition to be test fired and entered into IBIS.

Jennings breechface before treatment Jennings breechface after treatment

Jennings barrel bore before treatment Jennings barrel bore after treatment Case #3: This SKS type rifle was found buried in the backyard of a known gang member with a violent history. Local police believed this person might have been involved in two unsolved homicides in the Sacramento area where a weapon of this type was used. Police received a tip that the weapon was buried in the suspect’s backyard where they recovered the rifle and ten cartridges. The police recovered the gun and requested that it be test fired and entered into the IBIS database to search for possible associations. Note: the barrel bore was not photographed because a flash suppressor obstructed the area. IBIS results indicated a high confidence correlation with a 2004 Sacramento case and a 2002 Sacramento case. A firearms examiner has not yet confirmed these associations.

10

SKS breechface and firing pin area SKS breechface and firing pin area after before treatment treatment

SKS chamber area before treatment SKS chamber area after treatment

Practical Application of Rust/Corrosion Procedure in Identification Casework

A Jennings brand, model J-22, .22 Long Rifle caliber, semi-automatic pistol was submitted to the

laboratory with a request to determine if it had fired any of a number of expended .22 caliber lead bullets

and bullet fragments recovered from a shooting scene as well as from two decedents involved in the

incident. No cartridge cases were recovered from the scene of this double homicide. The pistol was

recovered from a storm drain where it had been left for several days after the shooting incident. The

general working condition of the firearm was assessed as well as the potential for successful association to

the fired bullets, given the presence of corrosion and rust deposits on the interior working surfaces.

11

The pistol had a chrome metal finish. Superficial rust, which could be easily wiped off, was observed on

the chrome surfaces under both grip plates. The exterior of the barrel displayed light rust. Rust deposits

were observed on the muzzle and inside the bore of the barrel. Inspection of the interior of the barrel with a

bore scope revealed localized deposits of scale-like rust distributed throughout the bore, which appeared to

occupy approximately 20% of the rifling surfaces. The rust/corrosion deposits were significantly heavier at

the muzzle end of the bore. A heavy coating of rust/corrosion was also observed at the forward edge of the

chamber and part way into the forcing cone area. The breechface surfaces, ejector, and firing pin were

corroded as well. The pistol magazine was also corroded. Rust deposits were observed on the exterior and

interior surfaces of the magazine. The corrosion was sufficient to cause the follower to become caught

against the sides after attempting to depress it about a quarter of an inch. However, it was possible to free

the follower sufficiently to use it with the Jennings pistol for test firing. Despite the corroded condition of

the Jennings pistol, the action operated in a normal manner with no signs of malfunction.

Jennings brand, model J-22, .22 Long Rifle caliber, semi-automatic pistol.

Jennings brand, model J-22 Jennings brand, model J-22

12

The pistol was field stripped and a Mikrosil cast of the entire interior of the bore and chamber of the pistol

barrel was prepared prior to test firing the pistol. The Mikrosil cast served the dual purpose of: 1)

supplementing the bore scope examination by allowing a thorough critical examination of the bore

surfaces; and 2) preserving a permanent record of the condition of the barrel bore surface prior to treatment

with Whink Rust Stain Remover. The cast was examined under the stereo microscope observation to

evaluate the condition of the rifling surfaces. The rifling along the entire length of the cast was examined

to determine if there were any lands or grooves that were completely free of rust deposits (i.e. clear

“channels” of corrosion-free rifling along the entire length of the bore). The rifling between the forcing

cone and the first two-thirds of the bore towards the muzzle was relatively free of corrosion deposits.

However, the remaining third of the bore closest to the muzzle appeared pitted with corrosion deposits.

There were no lands or grooves that were entirely free of corrosion, however, some were only minimally

marked with these deposits, such that with careful removal of this material, there appeared some potential

for revealing/preserving the bore’s signature in these areas.

Pre-treat vs. post-treat 11 o'clock 6X

Some pitting of the metal appears to be evident in forcing cone area only.

Rust and corrosion at the forcing cone has been significantly reduced with no detectable change in the tooling marks in the chamber, forcing cone and rifling in this area.

13

Pre-treat vs. post-treat 7 o'clock 20X

Rust and corrosion has been significantly reduced with no detectable change in the tooling marks in the rifling in this area. Note: The significant removal of corrosion deposits resulting in the restoration of

original tooling marks on the rifling beneath these deposits. This suggests that much of the corrosion had deposited over the tooling marks as opposed to directly pitting the metal surface itself in these areas.

The barrel and chamber were chemically treated to remove the corrosion deposits following the above

described procedure in an attempt to reveal/preserve the barrel bore surface comprising the “signature” of

the pistol prior to the deposition of the above described corrosion. The entire interior of the bore and

chamber was re-cast with Mikrosil after treatment. A post-treatment examination of the cast was

conducted to evaluate the effectiveness of the rust/corrosion removal process by comparing the post-

treatment cast with the pre-treatment cast using a comparison microscope.

As a result of this procedure, it was noted that much of the corrosion was deposited on the surface of the

rifling rather than permanent pitting caused by corrosion of the metal surface itself. Much of the corrosion

was successfully removed revealing little or no damage to the tooling marks on the surface of the affected

areas in the bore suggesting that much of the barrel’s signature had been revealed/preserved. There were,

however, some areas of corrosion sufficient to cause permanent damage to the metal surface (i.e. pitting),

thereby altering the barrel’s “signature” in these areas. This was most notable in the forcing cone area.

The pistol was reassembled and examined for general operability prior to test firing as previously

described. A total of six CCI brand, caliber 22 Long Rifle cartridges with 40 grain lead round nose bullets

Pre-treatment cast Post-treatment cast

14

(ammunition most likely to have been involved in the shooting incident) were successfully test fired from

the pistol into a water recovery tank.

The rifling impressions on all six test fired bullets were intercompared. These bullets exhibited sixteen

lands and grooves with a right twist. All six test fired bullets were successfully indexed and the land and

groove impressions were sequentially numbered. Further, all six test fired bullets exhibited sufficient

repetitive agreement of consecutive matching striae (CMS) 1 in the land impressions to establish an

identifiable signature of the Jennings pistol. Direct examination of the lands with a bore scope and of the

Mikrosil casts of the bore revealed an absence of subclass influence. 2 It was concluded that the lands were

highly individualistic tool working surfaces.

Additional agreement of CMS was also observed in the groove impressions; however, critical comparison

of duplicate Mikrosil casts of the barrel bore revealed prominent striae that survived the entire length of the

bore within the grooves. Compelling CMS agreement was observed when these prominent striae were

compared at each end of the bore casts. These observations suggested potential for subclass carryover in

the groove areas of the bore. Consequently, the groove areas were excluded as part of the individualistic

signature of the bore.

1 The author has adopted the conservative numerical criteria for identification of striated toolmarks proposed by Biasotti, AA, and Murdock J., Firearm and Toolmark Identification, Chapter 23, Vol. 2, pp 140 in Modern Scientific Evidence: The Law and Science of Expert Testimony, (Faigman DL, Kaye DK, Saks MJ, Sanders, J. eds., 1997). St. Paul: West, (unchanged on pp. 516 of 2002, 2nd Edition). The assessment of CMS in this case simply refers to a quantity of consecutive matching striae that repeat in the bullets test fired from the questioned pistol that exceeds the minimum criteria for striated toolmark identification to substantiate that the test fired bullets retain an identifiable signature that can be associated with the pistol. In this case the amount of agreement easily exceeded both the minimum requirements for 2D and 3D striated toolmark identification (i.e. 2 groups of 3X or 1 group of 6X for 2D and 2 groups of 5X or 1 group of 8X for 3D) 2To ensure that the markings on bullets test fired from the responsible firearm are individualistic, the author routinely evaluates the tool working surface(s) responsible for producing the signature of the firearm; in this case the rifling in the bore. Visual inspection using a bore scope supplemented with a Mikrosil cast of the bore is an effective way to accomplish this task. An excellent discussion of this general consideration in toolmark identification can be found on pages 241 –244 in the following reference: Miller, J., An Introduction to the Forensic Examination of Toolmarks, AFTE Vol 33, No. 3, Summer 2001 pp 233 –248. Additionally, Nichols specifically discusses the evaluation of barrel bore working surfaces in regard to potential for subclass influence on page 73 in the following reference: Nichols, R., Firearm and Tool Mark Identification: The Scientific Reliability and Validity of the AFTE Theory of Identification Discussed Within the Framework of a Study of Ten Consecutively Manufactured Extractors, AFTE Vol 36, No. 1, Winter 2004, pp 67 –88. Moran also discusses this consideration in the following reference: Moran, B., The Application of Numerical Criteria for the Identification in Casework Involving Magazine Marks and Land Impressions, AFTE Vol 33, No. 1, Winter 2001, pp 41 - 46

15

Prominent striae surviving the entire length of the groove impression, suggesting that these tool marks have

the potential to be created on bores made before and after the bore in question.

The test fired bullets were compared to a total of thirteen bullets and bullet fragments recovered from the

decedents and from the scene. One fragment was not marked with any rifling impressions and was of no

value for identification. Eight exhibited agreement of class rifling characteristics, however, were

insufficiently marked with striated markings for identification due to their damaged and fragmentary

condition. The remaining four bullets exhibited agreement of class rifling characteristics as well as

compelling agreement of gross shading and areas of CMS agreement with decipherable three-dimensional

(3D) contour.3 These bullets will be described as Bullets A, B, C, and D for descriptive purposes. A

3 Note that in truth, all striated marks are 3-dimensional. However, for the purposes of practical interpretation under the comparison microscope the following 2D and 3D definitions are offered to assist the examiner in the interpretation of CMS runs: 2D Striated Toolmarks: Any impressed or striated toolmark that lacks apparent depth or, 1) occupies only the very surface of a recording medium in which the toolmark appears, 2) have been made in a recording medium that is very thin, or 3) result from the application of the tool to the medium in such a way that only superficial markings are produced.

Examples of 2D striated surface toolmarks would include rubber wiper blade marks on a glass windshield; scratches in sheet film produced by dragging a glass microscope slide across it; markings resulting from dragging a fractured edge of a wooden tongue depressor over a sheet of carbon paper; or any other TM meeting these criteria.

3D Striated Toolmarks:

Forcing Cone Area Muzzle end of bore

Groove Located at 7 o’clock

16

critical tabulation of the areas of CMS agreement was conducted during the comparison of these four

remaining bullets as follows.

• Bullet A exhibited one area of CMS agreement that did not quite meet the conservative numerical

criteria for 3D toolmark identification (one clearly decipherable group of 4X and one group of 3X

that was not clearly decipherable in land impression #9). An inconclusive opinion was therefore

rendered in regard to whether the Jennings pistol fired this bullet.

• Bullet B exhibited several areas of significant CMS agreement that exceeded the minimum

numerical criteria for 2D and 3D toolmark identification in the groove impressions (two groups of

2X in groove impression #1, one group of 8X in groove impression #2, one group of 5X and one

group of 2X in groove impression #4, one group of 3X in groove impression #5, and one group of

4X and one group of 3X in groove impression #6). However, due to the subclass influence in the

grooves of the pistol as previously described, this quantity of agreement could not be used as a

basis for identifying the Jennings pistol as the source of the markings to the exclusion of all other

similarly marking firearms. Additional CMS agreement was observed in land impression #5 (one

group of 3X and one group of 2X), however this agreement did not meet the conservative

numerical criteria for 3D toolmark identification. An inconclusive opinion was therefore rendered

in regard to whether the Jennings pistol fired this bullet.

• Bullet C exhibited several areas of significant CMS agreement that exceeded the minimum

numerical criteria for 3D toolmark identification in the following land impressions:

One 3X group in land impression #1 (See figure 1) One 3X group in land impression #3 (See figure 2) One 5X group in land impression #5 (See figure 3) One 3X group and one group of 2X in land impression #8 (See figure 4)

It was concluded that this bullet was fired from the Jennings pistol based on the above described

agreement in the land impressions. Additional CMS agreement was observed in two of the groove

Any impressed or striated toolmark that displays discernable contour because the medium the toolmark is in has been displaced.

Examples of potential (any of these can also be 2D) 3D striated toolmarks would include striae appearing on fired bullets, striae produced from chisels and screwdrivers in wood or metal softer than the tool.

These definitions are used by Murdock and Moran for purpose of instruction in their Scientifically Defensible Criteria for Toolmark Identificatoin 12 hour Workshop. These definitions are expansions derived from original definitions offered by Biasotti, AA, and Murdock J., Firearm and Toolmark Identification, Chapter 23, Vol. 2, pp 133 in Modern Scientific Evidence: The Law and Science of Expert Testimony, (Faigman DL, Kaye DK, Saks MJ, Sanders, J. eds., 1997). St. Paul: West, (unchanged on pp. 498 of 2002, 2nd Edition).

17

impressions (one group of 6X in groove impression #2, and one group of 5X in groove impression

#5).

• Bullet D exhibited several areas of significant CMS agreement that exceeded the minimum

numerical criteria for 3D toolmark identification in the following land impressions

One 3X group in land impression #1 (See figure 5) One 6X group and two groups of 2X in land impression #9 (See figure 6) One 4X group in land impression #10 (See figure 7) One 3X group in land impression #11 (See figure 7) One 3X group in land impression #12 (See figure 8) One 3X group in land impression #13 (See figure 9)

It was concluded that this bullet was fired from the Jennings pistol based on the above described

agreement in the land impressions. No additional CMS agreement was observed in the groove

impressions.

In summary, two of the thirteen bullets and bullet fragments were identified as having been fired from the

Jennings pistol to the exclusion of all other similarly marking firearms. This evidence was presented in

court and supported by photomicrographs of the described areas. Photomicrographs of the comparison to

Bullet D are included in this paper for illustrative purposes.

Conclusion:

This procedure is successful in addressing superficial to minor rusting of the working surfaces of firearms

and is not intended as a method for “restoring” permanent damage to the working surfaces caused by

rust/corrosion. This procedure was successful in removing superficial rust adhering to the working surfaces

of firearms in several cases, including one specific case where the test fired bullets were successfully

identified to bullets recovered from a decedent and from the scene. This method appears to minimize the

permanent damage while successfully removing superficial rust/corrosion, thereby revealing/preserving

any surviving areas of the firearm’s signature that are not permanently altered due to pitting.

The authors caution that studies have not been conducted with regard to long-term storage of firearms

following this treatment process and recommend that sufficient test firing be conducted immediately

following the treatment to maintain the best possible exemplars for any future comparisons/identifications.

No research has been conducted at this time to determine any continued residual reaction of the Whink

Rust Stain Remover to assess the potential for continual degradation of the surfaces following the

treatment.

18

More extensive validation work needs to be conducted under controlled conditions, such as test firing a

firearm before and after rusting and subsequent rust removal treatment, and inter comparison of test firings.

This will be addressed in the future.

19

APPENDIX

Figure 1: SC-BRM-04 v T1 L imp 1 32X

Figure 2: SC-BRM-04 v T1 L imp 3 20X

3x

3x

20

Figure 3: SC-BRM-04 v T3 L imp 5 32X

Figure 4: SC-BRM-04 v T5 L imp 8 32X

5x

2x3x

21

Figure 5: 06-13 v T6 L imp 1 32X

Figure 6: 06-13 v T3 L imp 9 32X

3x

6x2x

2x

22

Figure 7: 06-13 v T3 L imps 10 & 11 20X

Figure 8: 06-13 v T3 L imp 12 32X

4x

3x

3x

23

Figure 9: 06-13 v T3 L imp 13 32X

Acknowledgement: The Authors wish to acknowledge the advice received from John Murdock to attempt the chemical removal of rust/corrosion on the firearm described in this case. This suggestion resulted in the identification of the firearm and lead to the discovery of the chemical process described in this paper.

Bibliography

1 Denio Dominic, “Making A Rusted Gun Functional,” AFTE Journal, Vol. 13, No. 3, 1981, pp 29 – 30. 2 Break Free an Armor Holdings Company, Product Catalog. http://www.break-free.com/. 3 Denio Dominic, pp 29 – 30. 4 Bates, J.S., “Cleaning of Rusted Firearms,” AFTE Journal, Vol. 5, No. 1, 1973, pp 11. 5 Brown, Cordell G., “Non-Destructive Rust Removal from Ferrous Objects,” AFTE Journal, Vol. 13, No. 4, 1981, pp 85 – 89. 6 Ibid 7 Williams-Sorensen, “Barrel Corrosion and its Effect on Identification,” AFTE Journal, NL13, 1971, pp 34 – 42. 8 Dutton, Gerard & Denholm, Steve, “Restoration of a .38 Calibre Belgian Revolver,” AFTE Journal, Vol. 31, No. 4, Fall 1999, pp 476 – 478. 9 Ibid 10 Ibid 11 Whink Products Company, http://www.whink.com/rust_stain_remover.htm

3x