Cross-Examination of Expert Witnesses

Michael DeBlis III, Esq.

Rule 702. Testimony by Experts

• If scientific, technical, or other specialized knowledge will assist the trier of fact to understand the evidence or to determine a fact in issue, a witness qualified as an expert by knowledge, skill, experience, training, or education, may testify thereto in the form of an opinion or otherwise, if (1) the testimony is based upon sufficient facts or data, (2) the testimony is the product of reliable principles and methods, and (3) the witness has applied the principles and methods reliably to the facts of the case

FRYE and DAUBERT tests

The “Sniffer” Machine • Dr. Vass and his laboratory stand to make a fortune selling

their contraption of a smell machine to law enforcement across the country. If this judge allows it in the case, many people including Dr. Vass stand to make a lot of money. Never before has a judge allowed it, but these people know that they have a damn good chance with this particular judge allowing this machine to be used in trial. Once Vass’s machine is used in trial, it validates and elevates the value of Vass’s invention. He and the lab can then sell it to every police department in the nation. When that happens, they are off to the races with the U.S. Patent Office with Dr. Vass’s machine.

What does all this mean to us in a courtroom?

• Expansion of pre-trial motions• Expansion of voir dire of experts• Real investigation of the science and the

scientist

Challenging the expert

• Either as to his or her credentials• The "expertise" itself• Use MOTIONS– You might not be able to keep out the testimony,

but you may be able to limit it

Don’t ignore investigating and challenging the expert

• Challenging the credentials• Three types of experts– Highly trained– On-the-job – Dubious training/dubious area

Strategy Considerations

Preparation of expert cross

• Learn something about the area– Inbau & Moensens, Scientific Evidence in Criminal

Cases • Use the phone• Get TRANSCRIPTS• Research– College texts– Read everything their expert has written

Interview the Expert Yourself

Experts and Language

• Learn theirs• Learn to translate for jury• Don't patronize

Basic Principles

• Normal principles of cross apply• Extensive preparation essential• Only ask leading questions• One fact per question• Never ask a question to which you do not

know the answer• Develop a system with that you are

comfortable with

Special Problems When Witness Is an Expert

• Witness is an expert in the field – you are not• Witness is more difficult to control than a lay

witness• Witness is likely well-educated and articulate• Witness is experienced at courtroom

testimony

Examples of Cross-Examination of Experts

• Forensic Pathologist in State v. Morehead• Radiologist in State v. Carey• Shaken baby syndrome experts in State v.

Carey

Forensic Pathologist

• State v. Morehead (client accused of strangling grandmother)– Defense was that grandmother died of heart

failure– Cross-examination of medical examiner was

critical to outcome– Examples of controlling the witness and learning

the terminology

Experts on the Shaken Baby Syndrome

• State v. Carey (client accused of shaking 5-month old baby causing brain damage)– Multiple expert witnesses for the state– Cross of radiologist who reviewed CAT scan and

MRI– Cross of non-treating outside expert on Shaken

Baby Syndrome

Cross-Examination

• What should jury feel about witness when you are done?– Is this good science? – Can they trust the witness?– Can they trust the evidence?– Can they rely on the evidence?

Examine Bias

• Who do they testify for?• Follow the money• Membership in groups• Built-in personal bias

Challenging the result

• Things not done cross• Result is not OBJECTIVE• Levels of certainty

Use demonstrative aids

Cross by learned treatise

The Ten Principles of Preparation for Cross of an Expert

• (1) Identify opinions that have to be challenged

• (2) Assemble all materials needed for cross-examination

• (3) Obtain complete CV of opposing expert• (4) Research expert’s prior testimony• (5) Investigate allegations of mistake or

misconduct

The Ten Principles of Preparation for Cross of an Expert

• (6) Research treatises and articles pertinent to the subject matter

• (7) Retain an expert• (8) Meet with opposing expert before trial• (9) Learn the pertinent terminology in the

subject matter• (10) Develop a system to organize your cross-

examination