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Chapter 15
Results of Examinations and Tests

Lie Detectors, Fingerprints, and Ballistics

Scientific Tests
     • Important Issues:
        • When can scientific tests be admitted to support a conviction?
        • When must they be admitted if favorable to the defense?

Scientific Evidence
    • Also called “Forensic” evidence:
        • Evidence which is prepared for use in a court of law
        • Subject to the usual requirements for evidence of relevance, materiality, & foundation, etc.
        • Must also show that it is “real” science, not “pseudo” science (scientifically valid)

Frye/Daubert Cases
    • Standards for scientific validity
        • Traditional rule: Frye v. U.S.
            • The process must be sufficiently established to have general acceptance.
                • This is usually established by the testimony of an expert in the field.
        • New rule: Daubert v. Merrell Dow
            • Daubert overrule Frye as it relates to federal cases only
            • Daubert rejected the stricted standard of Frye and adopted the looser standard of Federal Rule 702.
        • Daubert standard:
            • Scientific evidence is not excluded solely based on whether it is “generally accepted”
                • All valid tests are “new” at some point
            • Court instead determines two things:
                1. Will the expert testify to “scientific knowledge”?
                    • “Generally acceptance” is only one factor to be considered in determining this.
                    • Court can look at a number of other factors to determine if the science is valid.
                2. Will it be helpful to the jury?

    • Most states still follow the traditional (Frye) rule
    • All federal courts follow the federal (Daubert) rule

Polygraph Exams
    • Polygraphs (“Lie Detector” tests) continue to be controversial
    • There is no consensus on their reliability
        • Some test show they are, at most, only 87% accurate
        • Others show they are only 50% accurate- the same as random guess
    • Their accuracy depends heavily on the operator
        • The results can be subject to manipulation

    • Other concerns related to Polygraphs
        • The jury may abandon their role as “lie detectors” and put too much weight on the polygraph
        • Too much time may be consumed arguing about whether the test was valid and properly administered

    • Private use
        • used widely in private and public employment
    • This lead to the 1988 “Employee Polygraph Protection Act” (EPPA)
        • Prohibits most private employers from requiring a lie detector test as a condition of employment
        • Exception where employee is the “focus” of an investigation into loss of property of money

    • Court use
        • Most states and the military courts follow the “per se” rule that lie detector tests are inadmissible for all purposes.
            • New Mexico is the only state where they are generally admissible
    • Federal rules do not have a specific provision on the admissibility of Lie Detector tests
        • Admissibility varies from district to district

    • Federal approach to the Polygraph
        • Prior to Daubert, most districts followed the per se exclusion rule
            • The Eleventh Circuit was the only one that allowed limited use of the polygraph in rebuttal (U.S. v. Piccinonna).
        • After Daubert, most districts began allowing the same limited use
            • However, it is still expressly subject to exclusion if the probative value does not outweigh the consumption of time

    • May the parties stipulate to a lie detector test?
    • Is an offer or refusal to take a lie detector admissible?
    • If a prosecution witness fails a lie detector test, must the defense be informed under Brady ?

Blood Alcohol Testing
    • 3 types of tests in DUI’s for Blood Alcohol Level (BAL):
        • Blood alcohol test (most accurate)
            • Direct chemical test of the blood
        • Breath alcohol test (most common and convenient)
            • Breath alcohol is tested and then converted to an equivalent blood alcohol level
            • Not quite as accurate due to the conversion
        • Urine test (least accurate and least used)

    • Breath testing
        • Intoxylzer and the EPAS are the currently approved devices for evidentiary use in Cal.
        • Foundation:
            • Properly and regularly calibrated
            • Suspect was under constant visual observation for 15 minutes
            • Test was properly administered (new models are basically idiot proof).

    • Preliminary screening tests
        • May be used to develop probable cause to arrest, but not as evidence of the actual BAL
        • PAS (Preliminary Alcohol Screening)- handheld breath test device
        • HGN- Horizontal Gaze Nystagmus- officer observes tracking of the pupil

    • Legal Limits of Blood Alcohol for driving
        • California
            • .08% of alcohol in blood- impaired for driving purposes
            • .05% illegal to drive if under 21
        • All states have a limit of at least .10% and most now have .08%
        • National Highway Traffic Safety Administration now recommends .08%

    • “Implied Consent” statutes
        • By getting a license, a person is deemed to have consented to blood alcohol testing upon demand by law enforcement
            • Officer must have “probable cause”
        • Thus, a suspect does not have a right to:
            • Refuse to test under the 5th Amendment
            • Talk to an attorney before testing
            • Demand to be taken to a certain hospital or doctor
        • The suspect may choose blood, breath, or urine.

    • Penalty for refusing:
        • License suspension or revocation
        • Jury is instructed that the refusal may be considered as “consciousness of guilt”
    • Arrest must be determined to be legal and the probable cause adequate
    • Suspect must have been warned of consequences

Other Scientific Tests
    • Other scientific tests which have been found valid and acceptable:
        • DNA testing
        • Blood grouping and enzyme testing
        • Fingerprint comparison
        • Ballistics testing
        • Speed Radar
        • Neutron Activation Analysis

    • Scientific tests which have been found not valid or acceptable:
        • “Truth serums”
        • “Voice prints” (Voice Spectrographic Analysis)

    • When must a scientific test be admitted where favorable to the defense?
        • When defendant’s evidence is being excluded, the court must consider if there is a 6th amendment violation.
            • It depends on whether the exclusion “significantly undermines fundamental elements of the accused’s defense”.

    • For example
        • Polygraph- does not “implicate a significant interest” so may be excluded even if favorable
                                                                                            (U.S. v. Scheffer, US Supreme Court)
        • Hynoptically refreshed testimony-
            • Commonly excluded
            • However, if it is the only recollection the defendant has of the crime, the accused does have a significant interest in her defense at stake.
                                                                                         (Rock v. Arkansas, US Supreme Court)