The challenges of storing evidence, like with anything else, has to do with funding, with space, and with environmental controlled
A wide host of overarching limitations affect the efficacy of crime laboratories throughout the country. Most labs are underfunded, understaffed, and overwhelmed by sizeable backlogs. In an effort to maximize time and resources, forensic laboratories generally find themselves performing evidence triage, prioritizing by type of crime and/or by the need for the results for a legal proceeding.
Because of funding limitations laboratories tend to work on high profile or violent crimes before tackling other cases, such as crimes involving only property. A National Institute of Justice report found that a large amount of evidence remained untested in laboratories all over the country. Laboratories reported that in 14% of open homicide case evidence had not been tested. The same was true for 18% of open rape cases, and 23% of open property crime cases.
Reported reasons for untested evidence reveal that more than ¼ of it is due to funding limitations:
Improper handling or storage of evidence can have a dramatic effect on test results. Being familiar with chain of custody limitations and proper storage techniques, as well as the findings in a lab report, helps an attorney know which questions around the handling of evidence might be useful to raise.
From the moment a piece of evidence is identified, it must be handled in a safe and careful manner. It needs to be sealed and labeled, with all movements vigilantly documented. Rules governing the transportation and custody of evidence must be strictly maintained to ensure proper admission into a courtroom.
Limitations are inherent in the system of tracking and storage of evidence. With the level of detail required for maintaining guidelines, human error is a distinct possibility. One can well imagine that the amount of evidence delivered to a lab is often beyond the storage capacity of its facilities.
Sample storage procedures are designed to preserve the probative value of evidence. Proper storage prevents samples from being contaminated, destroyed, or lost, which safeguards the possibility for future testing.
Proper storage also requires appropriate cataloguing, tracking and labeling of evidence, and placement in the correct location, so it can be found when needed and not mistaken for other evidence in custody.
Additionally, every piece of evidence needs to be logged when it is removed from, and subsequently placed back into storage; chain of custody must be maintained. Logs should also indicate the quantity of sample being removed for each test. In some cases, the defense counsel has plausibly contended that part of a sample was unaccounted for, suggesting that it may have been planted to falsely incriminate an accused.
After a case is closed, or after a fixed amount of time, labs often destroy or get rid of evidence. In some states, limitations on such destruction are controlled by statute.