Some key case laws and rules of evidence that deal with forensic science

Introduction

Forensic science plays a crucial role in the criminal justice system. It provides scientific methods and techniques to assist in solving crimes. It also helps uphold justice. Over the years, courts have increasingly relied on forensic evidence to establish facts and ensure fair outcomes in trials. However, specific case laws and rules of evidence govern the admissibility and validity of forensic evidence. These laws aim to ensure that such evidence is reliable, relevant, and presented in a manner that respects legal standards. Legal professionals, forensic experts, and law enforcement need to understand fundamental case laws and rules. This understanding forms the foundation for how forensic science is integrated into the judicial process. This article examines some landmark case laws and explores essential rules of evidence. These have shaped the use of forensic science in courts.

Daubert v. Merrell Dow Pharmaceuticals, Inc. (1993)

• Significance: This landmark U.S. Supreme Court case established the “Daubert standard” for determining the admissibility of expert witness testimony, including forensic science. The ruling emphasized that scientific evidence must be relevant and reliable and that judges should act as gatekeepers in evaluating the validity of the methods and principles underlying the evidence.
• Criteria: The court outlined several factors to consider:
• Whether the theory or technique can be tested.
• Whether it has been subjected to peer review and publication.
• The known or potential error rate.
• The existence and maintenance of standards controlling the technique’s operation.
• Whether the method is generally accepted in the relevant scientific community.

Frye v. United States (1923)

Prior to Daubert, the Frye standard was the prevailing rule for the admissibility of scientific evidence. The case involved the admissibility of a polygraph test, and the court ruled that scientific evidence is admissible only if the methodology or scientific principle has gained “general acceptance” in its relevant field.

Impact: While some states still adhere to the Frye standard, many have adopted the Daubert standard. Frye remains influential in discussions about the admissibility of newer scientific techniques.

Federal Rules of Evidence (FRE)

• Rule 702 – Testimony by Expert Witnesses: This rule governs the admissibility of expert testimony, including forensic evidence. It states that an expert witness may testify if:
• The expert’s knowledge will help the trier of fact understand the evidence or determine a fact in issue.
• The testimony is based on sufficient facts or data.
• The testimony is the product of reliable principles and methods.
• The expert has reliably applied the principles and methods to the facts of the case.
• Rule 703 – Bases of an Expert’s Opinion Testimony: This rule allows experts to base their opinions on facts or data that they have been made aware of or personally observed. These can include information that may not be admissible in court, as long as it is of a type reasonably relied upon by experts in the particular field.

Melendez-Diaz v. Massachusetts (2009)

This U.S. Supreme Court case dealt with the Sixth Amendment’s Confrontation Clause, which gives defendants the right to confront witnesses against them. The ruling established that forensic analysts must be available to testify in person at trial rather than simply submitting written reports. This decision emphasized the importance of cross-examination in assessing the validity of forensic evidence.

Kumho Tire Co. v. Carmichael (1999)

This case extended the Daubert standard to include not only scientific testimony but also technical and other specialized knowledge. The ruling confirmed that the Daubert criteria apply broadly to all expert testimony, regardless of whether the field is purely scientific.

Williams v. Illinois (2012)

This Supreme Court case addressed the admissibility of forensic DNA evidence and the Confrontation Clause. The court ruled that an expert witness could testify about the results of DNA testing performed by another analyst without violating the defendant’s right to confrontation, under certain circumstances.

People v. Wesley (1986)

This case is one of the first to admit DNA evidence in a U.S. court. The ruling set a precedent for the admissibility of DNA testing results, paving the way for its widespread use in criminal trials.

Brady v. Maryland (1963)

This case established the Brady Rule, which requires the prosecution to disclose any exculpatory evidence, including forensic evidence, to the defence. Failure to do so can result in a violation of the defendant’s due process rights.

The Innocence Project Cases

While not a single case has been addressed by the Innocence Project, the work has brought attention to the misuse or misinterpretation of forensic evidence, leading to numerous exoneration. These cases highlight the importance of accurate forensic practices and the potential for wrongful convictions when forensic evidence is mishandled or misunderstood.

These case laws and rules collectively shape how forensic science is used and scrutinized in the courtroom. They ensure that the evidence presented is both scientifically valid and fairly evaluated.