Relevance Material - The evidence must relate to the case at hand. Previous criminal records are not material, and they can be prejudicial; as such, they are inadmissible. Probativeness - The evidence must prove something. If the evidence, such as the possession of a poison by the accused, has no relevance to a death by strangulation, it is inadmissible.
Competence Prejudice - Anything that unduly affects the trier-of-fact in an opinion either for or against the accused, is considered prejudicial. Prior criminal records, or inflammatory images may therefore be ruled inadmissible.
Competence Constitutional Constraints - The 4th Amendment to the U.S. Constitution states the following: The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no warrants shall issue, but upon probable cause, supported by oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized. As such evidence obtained without a warrant, without probable cause, and not listed in the warrant as the place, person, or thing to be seized, is therefore inadmissible, regardless of relevance.
Constitutional Constraints The following Amendments to the U.S. Constitution are important in terms of criminal proceedings: Amendment IV The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no warrants shall issue, but upon probable cause, supported by oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.
Amendment V No person shall be held to answer for a capital, or otherwise infamous crime, unless on a presentment or indictment of a grand jury, except in cases arising in the land or naval forces, or in the militia, when in actual service in time of war or public danger; nor shall any person be subject for the same offense to be twice put in jeopardy of life or limb; nor shall be compelled in any criminal case to be a witness against himself, nor be deprived of life, liberty, or property, without due process of law; nor shall private property be taken for public use, without just compensation.
Amendment VI In all criminal prosecutions, the accused shall enjoy the right to a speedy and public trial, by an impartial jury of the state and district wherein the crime shall have been committed, which district shall have been previously ascertained by law, and to be informed of the nature and cause of the accusation; to be confronted with the witnesses against him; to have compulsory process for obtaining witnesses in his favor, and to have the assistance of counsel for his defense.
Amendment VII In suits at common law, where the value in controversy shall exceed twenty dollars, the right of trial by jury shall be preserved, and no fact tried by a jury, shall be otherwise reexamined in any court of the United States, than according to the rules of the common law. Amendment VIII Excessive bail shall not be required, nor excessive fines imposed, nor cruel and unusual punishments inflicted.
Amendment XIV Section 1. All persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States and of the state wherein they reside. No state shall make or enforce any law which shall abridge the privileges or immunities of citizens of the United States; nor shall any state deprive any person of life, liberty, or property, without due process of law; nor deny to any person within its jurisdiction the equal protection of the laws.
Competence Statutory Constraints - This is also called "Privileged Information," or information told to a person who cannot reveal it (such as lawyers or clergy). Hearsay - Hearsay is a statement made outside of court by a person who was not under oath when the statement was made, but is then being used as proof that the statement was truth.
Frye Standard - 1923 Frye Standard (1923) During Fryes murder trial, he wanted his blood pressure test results (a precursor to a lie detector) used as evidence, but as it was not accepted by the scientific community as a reliable test, it was not admissible in court. The Frye Standard, or Frye Test, asks 1. Is the scientific theory generally accepted in the scientific community? 2. Is the scientific method generally accepted in the scientific community? 3. Has the technique been applied correctly?
Federal Rules of Evidence - 1975 Federal Rules of Evidence (1975), Rule 702 was a bit more relaxed, stating that if the witness expertise helps the "trier of fact" to understand the evidence, than a witness testimony would be considered admissible.
Daubert vs. Merril Dow - 1993 Daubert vs. Merril Dow (1993) The Supreme Court decided that it was the role of the trial court to be a "gatekeeper," and that its gatekeeping function was to make sure that scientific testimony and evidence are reliable and relevant. The Daubert Standard, or Daubert Test, asks: 1. Has the scientific theory or technique been tested? 2. Has the scientific theory or technique been subjected to peer review and publication? 3. What are the known or potential error rates of the theory or technique when applied? 4. Do standards and controls exist, and are they maintained? 5. Has the theory or technique been generally accepted in the relevant scientific community?
Expert Witness Forensic Evidence relies upon the testimony of expert witnesses. Expert witnesses are judged to be expert only by the Judge her/himself. In order to be so judged, it is necessary to have the appropriate training and experience (which need not be a Ph.D.), as when a mechanic gives expert testimony regarding a car involved in an accident. A non-expert witness is called a lay witness.
Expert vs. Lay Differences between an expert and a lay witness: 1. An Expert Witness must be qualified as an expert every time she/he testifies in court. 2. An expert witness is permitted to offer opinions, whereas a lay witness generally cannot.
Lab Reports Although lab reports are technically an example of hearsay, as the report itself cannot be cross- examined. There are, however, exceptions: in some states both sides can agree to admit it (stipulate), some states require the author present, in some states it fits under a business records exemption.
Defense vs. Prosecution Innocent until proven guilty . . .Reasonable Doubt - The Prosecution has the burden of proof. The defense has the responsibility to either exonerate the accused, or at least to introduce a reasonable doubt. Beyond aReasonable Doubt vs. No Doubt (The jurors must decide . . .). There is no precise definition, so it is thus in the hands of the jury. Defense must provide a spirited defense, regardless of the guilt or innocence of the accused (or a mistrial can be called). The Prosecution tries cases it can win (Winnability vs. The Desire to Seek Justice)
Discovery Motions The defense is required access to the witness list, as well as to the evidence, so that it may carry out its own evaluation of the evidence.
Chain of Custody & Evidence Contamination The chain of custody, if not carefully managed, not only increases the risk of contamination, but it also can introduce a reasonable doubt.