Chain of Custody: When Evidence Handling Sinks a Case

In April 2017, after years of litigation, 21,587 drug cases in Massachusetts were set to be dismissed. The evidence in those cases had gone through the state's Hinton drug lab, where chemist Annie Dookhan had tampered with and fabricated test results. Dookhan was convicted in 2013. The drugs had been seized and tested, but nobody could trust the record of what had happened to them in the lab.

That is an extreme case, but it shows what the chain of custody protects. Evidence is only useful if the jury can trust that the item tested is the item collected, and that nothing changed along the way. Here is how that record works, how it gets challenged, and what courts actually do when it has gaps.

What the chain records

The chain of custody is the chronological paper trail showing who collected, handled, transferred, analyzed and stored a piece of evidence, and when. It starts at the scene. Investigators photograph an item before moving it, record where it was found, package and seal it, and give it an identifying number. Each person who takes custody after that is recorded.

Take a hypothetical knife found at a homicide scene. An officer collects it and seals it in a container. A technician signs it out, takes it to the lab and lifts fingerprints. An evidence clerk then stores the knife and the lifted prints and logs everyone who checks them out. If any of those handoffs is missing from the record, the defense can ask who had the knife and what happened to it.

A properly marked evidence package shows the case number, the exhibit number, a description, where and when the item was collected, and the collector's name and signature, closed with a tamper-evident seal. A broken or undocumented seal is one of the first things a defense lawyer looks for.

Why some evidence needs it more

Not every item needs a complete chain. A gun with a serial number, or an object with distinctive marks that a witness can recognize, can often be identified on sight. Federal Rule of Evidence 901 allows identification by an item's "appearance, contents, substance, internal patterns, or other distinctive characteristics."

Fungible evidence is different. A bag of white powder looks like any other bag of white powder, so the prosecution has to show that the substance the lab tested is the one taken from the defendant. That is why so many chain-of-custody fights happen in drug cases, and why a lab like Hinton can undermine thousands of them at once.

Biological evidence raises its own problems. It can degrade or be contaminated if it is packaged, stored or handled badly. In the 1995 O.J. Simpson murder trial, LAPD criminalist Dennis Fung acknowledged that blood evidence had been collected in plastic bags rather than the recommended paper bags and kept in a police van without refrigeration for up to seven hours. The defense built much of its case around how the evidence was handled, and the jury acquitted Simpson.

What the law actually requires

In federal court, the governing rule is Federal Rule of Evidence 901, and most states have a similar rule. Before an item is admitted, the party offering it "must produce evidence sufficient to support a finding that the item is what the proponent claims it is." A witness who recognizes the item can do that. For fungible evidence, the chain of custody usually does it.

Here is the part television gets wrong. A gap in the chain does not automatically get evidence thrown out. In Melendez-Diaz v. Massachusetts, decided June 25, 2009, the Supreme Court noted that "gaps in the chain [of custody] normally go to the weight of the evidence rather than its admissibility." In most cases the judge admits the item, and the defense uses the gaps to argue to the jury that it should not be trusted.

The same footnote addressed who has to testify. It is not the case, the Court said, that everyone whose testimony may be relevant to the chain of custody must appear in person. The prosecution decides which links to prove, but whatever testimony it introduces must be given live if the defendant objects.

Exclusion happens when the problems are serious enough that the judge cannot find the item is what the prosecution says it is, such as a missing link at a critical point or signs of tampering. The defense usually raises that through an objection or a pretrial motion to exclude. A motion to suppress, strictly speaking, asks a court to exclude evidence on constitutional or statutory grounds, such as an unlawful search, rather than on authentication grounds.

The defense's tools

Finding a chain problem takes records: evidence logs, property receipts, lab bench notes and quality-control files. Under Brady v. Maryland, decided in 1963, the prosecution's suppression of evidence favorable to the accused violates due process when the evidence is material to guilt or punishment. Records showing that lab work was unreliable can fall into that category.

Those challenges also depend on having a lawyer who will make them. Gideon v. Wainwright, decided March 18, 1963, held that the Sixth Amendment's guarantee of counsel applies to the states in felony cases, so a defendant who cannot afford a lawyer must be given one. Strickland v. Washington, decided May 14, 1984, set the test for when that lawyer's work is so poor it violates the right: performance that is deficient, and a reasonable probability that, without the errors, the result would have been different. A failure to investigate an obvious problem with key evidence can be the basis for such a claim.

The burden never shifts. The defense does not have to prove that evidence was tampered with. It only has to raise enough doubt about the evidence that the jury is not convinced beyond a reasonable doubt.

When crucial evidence is kept out, or when its reliability collapses the way it did at the Hinton lab, the prosecution may have no case left. More often, the chain holds well enough to get the evidence admitted, and the fight moves to how much weight the jury should give it.

Sources

1. Federal Rule of Evidence 901: Authenticating or Identifying Evidence (Legal Information Institute)
2. Melendez-Diaz v. Massachusetts, 557 U.S. 305 (2009) (Legal Information Institute)
3. Motion to suppress (Legal Information Institute, Wex)
4. Brady v. Maryland, 373 U.S. 83 (1963) (Legal Information Institute)
5. Strickland v. Washington, 466 U.S. 668 (1984) (Legal Information Institute)
6. Gideon v. Wainwright, 372 U.S. 335 (1963) (Legal Information Institute)
7. ACLU of Massachusetts victory sets up single largest dismissal of wrongful convictions in nation's history (April 18, 2017)
8. Massachusetts Supreme Judicial Court to Vacate 21,587 Drug Conviction Cases (Innocence Project)
9. DNA evidence in the O. J. Simpson murder trial (Wikipedia)

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