CHALLENGING FORENSIC FIREARMS/TOOLMARKS EVIDENCE

CHALLENGING FORENSIC FIREARMS/TOOLMARKS

EVIDENCE

ACDLA “Loosening the Death Belt” Seminar

January 2010Joseph M. Saloom

Quick Outline Basics of Firearms/toolmarks examinations Possible sources of error Past defense strategies

Daubert Science of firearms/toolmarks identification Examiner qualifications

Most effective strategies Attacking the examiner’s qualifications Get your own expert Carefully review the evidence

Are there photographs? Are there drawings? Get all the notes and worksheets the courts will allow.

Definition: Toolmark

Features imparted on an object by the contact and force exerted from a tool. Two Types –

Impressed Toolmarks Striated Toolmarks

Fundamentals of Firearm & Toolmark Identification

Definition: Impressed Toolmark

Features produced when a tool contacts an object with enough compressive force that it leaves an impression.


Definition: Striated Toolmark Features produced when a tool contacts an object with lateral force and motion.


The Science of Firearm & Toolmark Identification is based on two fundamental propositions:


Proposition #1

Toolmarks imparted to objects by different tools will rarely if ever display agreement sufficient to lead a qualified examiner to conclude the objects were marked by the same tool. That is, a qualified examiner will rarely if ever commit a false positive error (misidentification).


Proposition #2

Most manufacturing processes involve the transfer of rapidly changing or random marks onto work pieces such as barrel bores, breechfaces, firing pins, screwdriver blades, and the working surfaces of other common tools. This is caused principally by the phenomena of tool wear and chip formation, or by electrical/chemical erosion. Microscopic marks on tools may then continue to change from further wear, corrosion, or abuse.


Range of Conclusions

Identification

Inconclusive

Elimination


Range of Conclusions - Identification

If the quality and character of the toolmark have sufficient detail, an identification can be concluded based on the correspondence of individual characteristics.


Examples of an Identification


Range of Conclusions - Inconclusive

If the quality and character of the toolmark are lacking, an examiner may not be able to make an identification or elimination. In this case an inconclusive result would be the appropriate response.


Examples of an Inconclusive


Range of Conclusions - Elimination

If significant disagreement in class characteristics exists, an elimination conclusion would be the appropriate response.

If disagreement in individual characteristics of an exceptional nature exists, an elimination conclusion may be the appropriate response.


Examples of an Elimination


TRADITIONAL CHALLENGES

Daubert or challenge of the science Examiner Qualifications Bias of the examiner Lack of documentation Type of conclusion Opposing Expert

Five Prongs of DaubertTestability General Acceptance Peer ReviewKnown or Potential Error RateMaintenance of Standards &

Controls

Daubert is a dead endFirearm & Toolmark Identification meets the reliability standard put forth by the Daubert decision because it :

is Testable is Generally Accepted is Peer Reviewed has Known Error Rates maintains Standards & Controls

Examiner Qualifications

How much experience does he/she have?

Where was the training received? What type of supervision on the job? Is the laboratory accredited? Is the examiner certified?

Examiner Bias

Is the examiner an employee of the submitting agency?

Was there more than one firearm or tool submitted?

Laboratory Documentation

What type of notes were taken at the scene or to describe the evidence?

Were there photographs of the evidence taken?

If there was a microscopic match, were there photographs or sketches made?

Can they produce the documentation?

Type of Conclusion

Was the identification “to the exclusion of all others”?

Was the conclusion an indeterminate or inconclusive?

What was the conclusion based upon?

Hire an opposing expert

Most attorneys do not have a scientific background.

Most attorneys do not have a firearms identification background.

Most attorneys do not feel comfortable questioning the state’s expert.

Best solution is to hire your own. An opposing expert can assist in assessing the evidence.

Important Websites for Information.

www.swggun.org Look for the Admissibility Resource Kit

(ARK) There are sites for admissibility rules,

court rulings, elements, and opposing viewpoints.

www.afte.orgThis is the Association of Firearms and

Toolmarks Examiners web page.

http://www.swggun.org/

http://www.afte.org/

CHALLENGING FORENSIC FIREARMS/TOOLMARKS EVIDENCE

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