Police investigators in Houston, looking into incompetence at the city's crime lab, have discovered 280 boxes of lost evidence, covering around 8,000 cases stretching all the way back to the late 1970s. How long do police departments usually hold onto evidence?
Anywhere from the closing of the case until the end of time. There are few state guidelines addressing the long-term storage of evidence, so decisions about how to handle the materials are usually left up to local prosecutors and police. Some departments are assiduous about destroying evidence, say, one year after a defendant has either been acquitted or sentenced; others hold onto evidence indefinitely, figuring that they're better safe than sorry. It is not unheard of, for example, for evidence storage facilities to warehouse boxes of drugs that are 40 years old, or biological detritus from murder cases solved during the Johnson administration. Evidence from open, or unsolved, cases is frequently kept around for that long, unless the investigating officer is diligent enough to see to the evidence's destruction once the statute of limitations has expired.
There are also departments that may have disposal policies in place, but lack the manpower to determine which evidence should be preserved, which should be destroyed, and which should be returned to its rightful owner. It's estimated that a case's worth of evidence takes an hour to log and mark for disposal, retention, or return; that means that the newly discovered Houston evidence would take one police officer four full years of research (40 hours a week, 50 weeks a year) to identify and clear.
The downside to quickly disposing of evidence, of course, is that critical items sometimes get sent to the incinerator too soon. But evidence that's kept for the long haul can tempt property clerks and other insiders into stealing valuables. Tales of sticky-fingered employees are legion: Recently, for example, several Memphis, Tenn., workers were charged with lifting $2 million worth of cocaine from an evidence storage room.
When evidence is ordered destroyed, the process is usually done through incineration with at least two people present. Guns are often melted down, while hard currency may be donated to a charitable fund. Items that belong to a victim are returned to their rightful owners, who may have just 90 days to come in and claim their property.
Despite the disparity in evidence retention approaches, police departments are becoming more and more careful about preserving DNA samples for the long term. At least 25 states now have statewide policies in place regarding how long evidence containing DNA should be retained. Whereas such evidence might have previously been destroyed once an incarcerated defendant's appeals were exhausted, it's now often kept for the duration of the sentence in case a post-conviction DNA test is ever requested.
Explainer thanks Joseph T. Latta of the International Association for Property and Evidence, and Blake Harrison of the National Conference of State Legislatures.