1. List out the steps involved in marking evidence.
    
2. Discuss how to authenticate crime scene evidence.
    
3. Describe the importance of the chain of custody of evidence, and how the chain of custody is established.
    
4. List out the steps involved in establishing the foundation for scientific evidence.
    
5. Answer the question of whether or not defendants are provided access to expert witnesses.
    
6. Describe the process of gathering fingerprint evidence.
    
7. Explain how blood alcohol testing works.
    
8. Discuss the significance of a ballistics test.
    
9. Explain why the results of polygraph examinations are generally inadmissible at trial.

SUMMARY: Forensic laboratory analysis is a crucial component of modern criminal investigation. These tests include DNA, blood analysis, fingerprints, and ballistics. Evidence found at the crime scene typically is sent to a crime lab for evaluation. Individual suspects also may be subjected to testing to determine whether there is a match with material seized at the crime scene.

Forensic evidence, though only a small percentage of the evidence introduced at trial, may be vital in the determination of guilt or innocence in cases ranging from drug possession to driving under the influence and sexual molestation. A number of these forensic tests are well established, and judges typically take judicial notice of their scientific reliability. In other instances, a foundation must be laid for admission of the results of the forensic evidence. A key aspect is establishing a chain of custody.

The foundation for the introduction of scientific evidence involves three questions: first, whether the test was scientifically valid; second, whether the equipment was accurate; and third, whether the test was performed in the required fashion by a qualified analyst.

Judges will accept the scientific validity of established scientific tests like fingerprinting by judicial notice. The validity of less well-established tests in most instances is established through expert testimony on voir dire.

A fingerprint is an impression left by the “friction ridges” of the human finger. A fingerprint typically is based on the last joint of fingers and thumbs. Fingerprint impressions may be left on a surface by secretions of sweat from the eccrine glands or may be by ink transferred on the skin to a fingerprint card. Fingerprints left at the crime scene are compared to fingerprints on a database to identify the perpetrator of a crime or to identify the name of a suspect in detention.

Blood tests may be used to measure the alcohol concentration in the blood to determine whether an individual is intoxicated. Blood type evidence also is used to determine whether there is a match between blood evidence at the crime scene and the blood type of the alleged perpetrator. DNA analysis provides definitive analysis of the perpetrator’s identity.

Various tests are used to identify whether a substance is an unlawful narcotic. Ballistics analysis may be employed for various purposes including whether a bullet was fired from a particular firearm.

Most courts hold that the results of polygraph examinations are inadmissible because they are considered unreliable and are thought to confuse jurors.

Experiments are used to replicate conditions to test the credibility of testimony.