Legal Definitions - CSI effect

The CSI effect, named after popular television shows like CSI: Crime Scene Investigation (where CSI stands for Crime Scene Investigation), describes how fictional portrayals of forensic science in media can influence the expectations and perceptions of jurors in real-life court cases.

This phenomenon suggests that jurors who regularly watch crime dramas or documentaries that heavily feature forensic techniques may develop unrealistic expectations about the availability, accuracy, and speed of scientific evidence. They might come to believe that every criminal case should produce definitive forensic evidence, such as DNA, fingerprints, or ballistic analysis, and that such evidence is always 100% conclusive. Consequently, if such evidence is not presented, or if it is not as clear-cut as seen on television, these jurors might be more reluctant to convict, even when other substantial evidence supports the prosecution's case.

Here are some examples illustrating the CSI effect:

• Case of the Missing Fingerprints: In a burglary trial, the prosecution presents strong eyewitness testimony, security camera footage placing the defendant at the scene, and possession of stolen goods. However, the defense emphasizes that no usable fingerprints were recovered from the point of entry. Jurors, influenced by crime shows where fingerprints are routinely found and used to identify suspects, might express doubt during deliberations, asking, "If he was there, why weren't his fingerprints found? The police must have missed something or the evidence isn't strong enough without them."

  This illustrates the CSI effect because the jurors are placing an undue emphasis on the absence of a specific type of forensic evidence (fingerprints), which they expect to be present in every crime, despite other compelling non-forensic evidence.

• The Expectation of DNA Evidence: During a sexual assault trial, the victim provides a detailed account, and the defendant's alibi is weak. While some DNA evidence was collected, it was degraded and inconclusive, only ruling out a large percentage of the population but not definitively identifying the defendant. Some jurors, accustomed to television shows where DNA evidence provides an infallible match, might be hesitant to convict, believing that "if the DNA doesn't prove it 100%, then there's reasonable doubt."

  This demonstrates the CSI effect as jurors expect perfect, conclusive DNA evidence as depicted in fiction, and its absence or ambiguity leads them to question the entire case, even with other strong evidence.

• Demand for High-Tech Solutions: In a complex arson case, investigators relied on extensive interviews, chemical analysis of accelerants, and structural engineering reports to determine the cause and origin of the fire. The prosecution presents expert testimony from fire marshals and chemists. However, some jurors might feel underwhelmed because there was no dramatic "computer simulation" of the fire's spread or a "trace evidence" expert revealing a unique fiber from the perpetrator's clothing, as often seen in fictional narratives.

  This exemplifies the CSI effect by showing how jurors might expect sophisticated, visually dramatic, and instantly conclusive forensic techniques from television, and may undervalue painstaking, less glamorous, but equally valid investigative methods used in real life.