Understanding the Federal Rules of Evidence: A Guide

In American courts, expert witness testimony is governed by evolving standards: the Frye standard (general acceptance test from 1927) required scientific techniques to gain majority acceptance within the relevant scientific community before admission, while the Daubert standard (codified in FRE 702) shifts gatekeeping responsibility to judges who must evaluate reliability through factors including testing, peer review, error rates, and controlled standards, allowing minority scientific opinions to be considered if they meet these criteria; however, implementation varies significantly across states, with some continuing to use Frye and others adopting Daubert, creating inconsistencies in how scientific evidence is admitted in criminal and civil proceedings.

Frye standard requires expert testimony to be based on generally accepted principles and methods. Daubert standard, increasingly used in federal and state courts, requires judges to determine: (1) Whether testimony is based on reliable facts or data; (2) Whether it uses reliable principles and methods; (3) Whether the witness applied those methods reliably to the specific case. Judges ultimately decide expert admissibility under Daubert, making it essential for evaluators to understand these standards when preparing testimony.

The Daubert and Frye standards are the two standards for what is acceptable for expert testimony in a court of law. They guide what science and what expert testimony can be admitted into courts. The Daubert standard is applied by federal courts and focuses on whether the scientific method was used, whether the theory can be tested, whether it has been peer-reviewed, and whether it has a known error rate. The Frye standard, used by many states, focuses on whether the scientific community generally accepts the methodology. These standards help ensure that expert testimony is reliable and based on sound scientific principles.

In Daubert v. Merrell Dow Pharmaceuticals, Inc., the Supreme Court held that the Federal Rules of Evidence implicitly overturned the Frye standard. The Daubert standard provides four factors for courts to determine admissibility: (1) whether the expert's theory or technique can be tested and has been tested, (2) whether the theory or technique has an acceptable known or potential rate of error, (3) whether there exist standards controlling the technique's operation, and (4) whether the theory or technique has attained general acceptance. Currently, 22 states in the US have adopted this standard for analyzing expert witness rules.

The Frye standard (general acceptance test) allows scientific evidence admissible only if it is generally accepted in the scientific community, while the Daubert standard (used in federal courts) requires judges to evaluate expert testimony based on specific criteria including testability, peer review, error rates, and scientific validity before determining admissibility.

A motion in limine is a pre-trial legal motion that prevents opposing counsel from introducing potentially inadmissible evidence or facts in front of the jury without first obtaining a court ruling on admissibility; unlike a traditional objection which occurs during trial, a motion in limine addresses facts that could unfairly prejudice the jury before they become part of the trial record, and when violated, attorneys must decide whether to pursue a mistrial or seek a jury instruction to disregard the improper evidence.

Trial objections are procedural devices used to notify the court of improper conduct during testimony, serving two main purposes: keeping opponents following rules and preserving issues for appellate review; objections must be timely (made immediately at the moment of the infraction) and specific (stating clear legal grounds), and attorneys should have a cheat sheet of common objections ready for quick reference during fast-paced testimony, with the 18 most common objections including relevance, vague and ambiguous questions, speculation, leading questions, lack of foundation/personal knowledge, non-responsive answers, compound questions, hearsay, improper lay opinion, assumes facts not in evidence, misstates evidence, argumentative questions, narrative, repetition, undue prejudice, character evidence, and beyond the scope.

Motions in limine are typically filed in large numbers because parties want to exclude as much unfavorable evidence as possible. Parties know they won't win on all motions, so they file many to maximize the chance of excluding some evidence. This is standard practice in complex litigation. Judges typically handle evidence objections at trial rather than pre-trial, unless the evidence would so prejudice the jury that they couldn't make a fair decision. Parties raise objections during trial when evidence is presented, and judges make rulings in sidebar conferences or chambers. This allows judges to assess the actual impact of evidence on the jury.

Motions in limine are evidentiary motions filed before trial to either exclude or include certain evidence at trial. The defense may file motions to preclude references to prejudicial information (such as hearsay about events in Aruba or between Karen and Higgins) that would be more prejudicial than probative. The court rules on these motions outside the presence of the jury before trial. These motions help ensure that only relevant and admissible evidence is presented during the actual trial. The defense noted that the Commonwealth had made an additional TRO request to the US Attorney's Office on Friday, which could take 'another couple of weeks' to resolve, further complicating the discovery timeline.

Motions in limine are pre-trial motions made to exclude certain evidence from trial or to include certain evidence. The host analyzed how the defense argued that certain evidence should not be admitted without proper chain of custody and metadata. The analysis examined how the judge serves as the gatekeeper for what evidence can be presented to the jury, and how motions in limine help establish the boundaries of what will be allowed during the trial. This demonstrates the procedural mechanisms for controlling evidence at trial.

California's Evidence Code differs significantly from the Federal Rules of Evidence in several key areas: (1) Relevancy standards—California requires facts to be in dispute, while federal rules accept facts of consequence; (2) Public policy exclusions—California bars expressions of sympathy and certain offers to pay medical expenses that federal courts may admit; (3) Character evidence—California allows specific instances of victim character while federal rules limit to opinion/reputation; (4) Hearsay exceptions—California has stricter requirements for dying declarations (actual death required) and broader exceptions for child abuse statements; (5) Authentication—California uses a secondary evidence rule instead of the federal best evidence rule; (6) Scientific evidence—California focuses on general scientific acceptance while federal courts apply the Daubert five-factor test; (7) Polygraph tests—Federal courts allow them under notice requirements while California prohibits them.

Evidence is relevant if it has any tendency to make a fact more or less probable than it would be without the evidence, and that fact must be of consequence in determining the action; under both the Federal Rules of Evidence (Rule 401) and California Evidence Code Section 210, relevant evidence is admissible unless excluded under specific rules like Rule 403 (federal) or Section 352 (California), which allow courts to exclude evidence when its probative value is substantially outweighed by concerns such as unfair prejudice, confusion of issues, misleading the jury, undue delay, waste of time, or cumulative redundancy.

When answering evidence questions, always include an introduction stating whether California Evidence Code or Federal Rules of Evidence apply. California distinctions are highlighted in red in the materials. If the question does not specify 'answer according to California law,' assume federal rules apply.

The Federal Rules of Evidence (FRE) are the primary rules of evidence used in federal courts, and most states have adopted similar rules. For example, Michigan uses the Michigan Rules of Evidence (MRE), which closely mirror the FRE. This means that evidence rules are largely consistent across different jurisdictions, making legal education focused on federal rules applicable to most state courts. Understanding these rules is essential for anyone involved in legal proceedings.

Most states use the federal Rules of Evidence, though states have their own rules. The federal Rules of Evidence are a very good starting point to learn Rules of Evidence. They are broken down subject by subject.