Evidence: Origins, Types, & Admissibility

Evidence refers to information or objects that may be admitted into court for judges and juries to consider when hearing a case.

Rules of Evidence

Information that is court approved (good science, relevant, correctly collected, thoroughly documented) that is used to determine guilt or innocence is evidence. The rules of evidence are used to determine whether something is admissible or inadmissible. This serves to screen out or exclude irrelevant or prohibited evidence.

The rules of evidence are applied to determine the admissibility of all information, such as:

• Eyewitness testimony
• Photographs
• Physical objects
• Scientifically generated information like DNA

If the information survives, it can be accepted as evidence of a material fact in the ensuing trial. Ultimately, forensic (and other types) of evidence are used to reconstruct the events of a crime.

Admissibility

A key pre-requisite of admissibility for any piece of information is a solid supportive foundation for any offer of evidence. There must be enough information to convince a judge that the proposed time of evidence may in fact be true.

Admissible evidence must be:

• Reliable
• Relevant to the case at hand
• Scientifically acceptable

Admissibility Hearings

Admissibility hearings provide a way for new scientific methods to be introduced and accepted as viable tools in forensic science. The can be held during the presentation of the case or separately.

The standards used by courts can vary by jurisdiction, these are some important ones:

• The Frye Decision and Frye Standard
• The Federal Rules of Evidence
• Daubert Decision (1993)
• The Trilogy

The Frye Decision and Frye Standard

In 1920, Mr. James Frye was charged with second-degree murder in the shooting death of a physician named Dr. Robert W. Brown. The defense attempted to get an expert to testify that Mr. Fyre had taken, and passed, a lie detector test.

The judge disallowed the testimony:

• Rejected the scientific validity of the lie detector test due to the novel nature of the newly developed technology
• Fyre was convicted

He appealed but the decision was upheld and the Fyre Standard was developed. The Fyre Standard established the criteria known as general acceptance. To meet the Fyre Standard the court must decide whether the questioned procedure, technique, or principle is “generally accepted” by a meaningful segment of the relevant scientific community.

When a test has not gained scientific recognition from psychological and physiological authorities, expert testimony regarding the results of such a test is inadmissible.

The Federal Rules of Evidence

Rule 702 was a minor step forward from the Fyre Standard. “Testimony by Experts” stated: 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.

The evolution from generalists to specialists, makes the ‘general acceptance’ more difficult to obtain. Rule 702 made it a little easier.

However Rule 702 did not specify how a witness was qualified or what, specifically, the court should weigh when making that assessment.

Daubert Decision (1993)

Daubert vs Merrell Dow Pharmaceuticals

• Jason Daubert and Eric Shuller were born with serious birth defects
• They, and their parents, believed that a morning sickness medication, Bendectin, was responsible
• Both sides submitted scientific evidence which reached different conclusions

The Supreme Court ruled that general acceptance is not an absolute requirement for determining admissibility. The decision also established the role of a trial judge as the gatekeeper.

Daubert and Shuller’s expert testimony was disallowed for not using acceptable scientific methods. The Supreme Court also offered suggestions for making the determination, while leaving some flexibility to the judge. The five factors the court may consider are:

• Has the technique been tested in actual field conditions?
• Has the technique been subject to peer review and publication?
• What is the known or potential rate of error?
• Do standards exist for the control of the technique’s operation?
• Has the technique been generally accepted within the relevant scientific community?

The Trilogy

The trilogy are three decisions which significantly impacted the way evidence admissibility is addressed.

1. Daubert
   • Established the judge as the gatekeeper
2. Joiner (General Electric Company vs. Joiner)
   • Employee claimed that the chemicals he was exposed to at work gave him cancer and wanted to have animal studies submitted to support his case
   • The court rejected these studies because they focused on:
     • Different chemicals
     • Different exposure levels
   • Evidence must pass Daubert criteria and relevance test
3. Kumho (Kumho Tire Company vs. Carmichael)
   • Civil case centered on the responsibility of the tire company in a fatality that resulted from an accident attributed to tire failure
   • One expert witness was an engineer, and the court ruled that the testimony offered by the engineer fell under the umbrella of scientific expert
   • Kumho extended the Daubert ruling to all experts (not just scientists)

Categories of Evidence

Inclusive vs. Exclusive

Inclusive evidence

the evidence is included in the population of items that could have been the source of the evidence in question

Exclusive evidence

the evidence is excluded from the population of items that could have been the source of the evidence in question

Direct vs. Circumstantial

Direct evidence

Is that which is known to a person by personal knowledge, such as eyewitness testimony.

Circumstantial evidence

Is evidence that requires inference to move logically from the information provided to the answer to a question (evidence must still be tied to the suspect)

Reconstruction Evidence

Direct evidence

Is that which is known to a person by personal knowledge, such as eyewitness testimony.

Reconstruction evidence

Provides information about the events preceding, occurring during, and occurring after commission of a crime

• Useful if a suspect admits to being present, but denies involvement
• Involves scientific principles, but also requires logic, observations, experience, and witness statement evaluation.
• Associative evidence: associate or dissociate a suspect to a crime
• Exemplar: a sample of known origin used as a reference

Class vs. Individual

Class Characteristic Evidence

Does not reference a particular suspect; it has the ability to narrow a field down to a group

Individual Characteristic Evidence

Does associate a particular individual with the commission of a crime; it has the ability to pin point a source

The ultimate goal of forensic science is to link a potential offender to a crime scene

• Individual evidence is ideal
• Class evidence is still extremely important
• Class evidence is typically examined based on inclusiveness or exclusiveness

The type of evidence is important, but the significance of the evidence cannot be understated, The significance depends on a variety of factors:

• Biology
  • Focus on human tissues
  • DNA/Blood grouping
• Chemistry
  • Seized drugs
  • Toxicology samples
  • Explosives
• Trace
  • Locard’s exchange principle
• Fingerprint
  • Latent (invisible) print development
  • Print identification
• Impression
  • Footwear
  • Tire treads
• Firearm and Toolmarks
  • Fired bullets
  • Cartridge casings

Quiz