What specific impact does a break in the chain of custody have on the admissibility of evidence in court?

A break in the chain of custody compromises the integrity and authenticity of evidence, potentially rendering it inadmissible in court. The chain of custody is the documented chronological record of the seizure, custody, control, transfer, analysis, and disposition of evidence, establishing its location at all times. If this chain is broken, it creates doubt about whether the evidence presented in court is the same evidence collected at the scene, or if it has been altered, contaminated, or tampered with. For example, if a blood sample is collected at a crime scene but the documentation fails to show who handled it between the scene and the lab, or if the sample was left unsecured at any point, the opposing party could argue that the sample tested in the lab is not the original sample, or that it may have been contaminated, thereby challenging its validity. Admissibility hinges on proving that the evidence is what it is claimed to be (authenticity) and that it has not been altered in any significant way (integrity). A break in the chain weakens or destroys this proof, allowing a judge to rule the evidence inadmissible, meaning it cannot be presented to the jury or considered in reaching a verdict. The prosecution bears the burden of establishing a complete, unbroken chain of custody; failure to do so can lead to the exclusion of critical evidence, potentially impacting the outcome of the case.