Challenging the Chain of Custody in Criminal Trials

In criminal trials in Iowa, the prosecution has the burden of proving guilt beyond a reasonable doubt. It is the criminal defense lawyer's job to demonstrate that the prosecution cannot meet this burden. One way this can be done is by challenging the chain of custody of a key item of evidence.

The chain of custody is the documentation of who had control of an item of evidence, and where it was kept, continuously from the time it was seized by police to the time it is offered as an exhibit at trial. The chain of custody documentation is necessary to show the item presented in the courtroom is the same item police seized at the time of the arrest.

For example, if police seize a bag of marijuana during a search of the defendant's vehicle, the chain of custody documentation would typically show that after the arrest the officer gave the bag to another officer who placed it in the evidence locker. The documentation would also show when and by whom the bag was removed from the locker and brought to the courtroom for the trial. If this information is not adequately documented, the chain is said to be broken.

If the defense can show the chain of custody was broken, the court can rule the evidence in question is inadmissible.

Sometimes it is not possible to show a total breakdown of the chain of custody, but it is possible to raise questions about its reliability or cast doubt upon whether it was adequately documented. In these situations, the court may rule that the issues related to the chain of custody go to its weight, not its admissibility. The evidence will be admissible, but the defense can still argue to the jury that it is unreliable.

Source:, "How to Suppress Evidence," accessed Sept. 16, 2016

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