Automated sample storage systems follow NIST recommendations for long-term storage of DNA extract and trace materials.

Manually managing an extensive repository of evidentiary DNA samples and small biological samples can be time-consuming, contributing to a slowdown in overall laboratory efficiency. This issue is compounded in forensic laboratories by sample overcrowding due to legislation and best practice guidelines stipulating that DNA samples be retained throughout the incarceration period, until statute of limitations expiration or even indefinitely, depending on the crime and jurisdiction. Without proper sample storage controls in place, the risk to forensic labs reaches beyond lost time and diminished productivity. Any compromise to sample integrity can prolong or otherwise hinder forensic investigations and potentially contribute to an incorrect verdict rendered by the judge or jury. If sample integrity, handling or chain of custody is successfully challenged in court, the laboratory’s reliability is subject to future scrutiny; and in instances where widespread negligent sample storage practices come to light, media attention and public outcry can cause lasting damage to the forensic lab’s credibility and negative consequences for its management team.

Automated sample storage methods eliminate the risks and hassles associated with manual sample storage so that laboratories can efficiently manage, and accurately monitor, ever-expanding active and archived forensic sample libraries. By doing so, the storage process reliably complies with best practice guidelines, samples are protected from harmful environmental conditions, and analysts may refocus their time and efforts toward testing and analysis. Here, we discuss three ways that an automated system reduces risk and increases efficiency during long-term storage, defined as longer than 72 hours1, of DNA samples and small biological samples.

The case for automated environmental control

Recommended storage conditions differ depending on small biological sample type1. In the case of DNA, storage conditions range from freezing extracted DNA samples in specialized tubes for automated downstream processing, to embedding DNA in a solid paper-based matrix and storing at controlled conditions. Manual freezers are easily sourced with low upfront costs, and typically incorporate an auto-defrost or frost-free capability to eliminate ice buildup. This process, however, involves increasing the temperature above freezing several times per day, and these repeated freeze/thaw cycles are known to damage DNA2. Samples also risk damage from temperature gradients formed in crowded freezers and refrigerators if air flow is impeded, or when exposed to warm, ambient room conditions as users repeatedly open the unit to search for samples.

Automated sample storage systems follow NIST recommendations for long-term storage of DNA extract and trace materials, including temperature controlled (15 to 20 C), refrigerated (4 C) and frozen (–20 to –80 C) environments, and can be used for active case work or cold cases that are reopened decades later. In an instance of the latter, the Netherlands Forensic Institute (NFI) uses a –80 C BiOS automated storage system (Hamilton Storage) to store DNA extracts for up to 80 years, in compliance with government regulations. Temperature and humidity levels are continuously monitored and displayed, and when integrated with a forensic lab’s laboratory information management system (LIMS), real-time climate conditions can be stored and output for use during court depositions. Alarm functions automatically send notifications if the temperature falls outside of normal operating parameters, or if any system malfunctions occur. Sample identification, picking and storing steps occur at the same temperature to eliminate risk of DNA damage from freeze/thaw cycles in cold storage.

The case for automated chain of custody control

Evidence control, by means of an intact chain of custody, is a critical factor toward the objective application of forensic science in the criminal justice system. The risks of transcription mistakes, accidentally or intentionally unlogged actions or information, and other human errors are ever-present when manually documenting all pertinent sample, location and custodial information. When stored in locations with communal access, DNA-containing evidence or other small biological samples are at risk of unauthorized access and movement, misplacement, cross-contamination, premature destruction, tampering or even theft. Many of these risks would not come to light during routine sample storage audits, yet the consequences are significant. A broken chain of custody could result in case delays, the need for retesting, inadmissibility of evidence, and incorrect verdicts along with the aforementioned harm to the laboratory’s reputation.

Conversely, automated sample storage methods also automatically document the chain of custody process. Instead of manual documentation that is prone to human errors, two-dimensional barcodes on sample containers are used with an automated storage system to precisely track all information associated with the sample throughout its life, even when stored for decades and during employee turnover. This includes case, type, location, status, date/time, custody access and transfer, and originating evidence, if aliquoting from a larger, parent sample into smaller, child volumes. Security features restrict sample access to authorized users assigned to the specific case, and hands-free robotic sample picking eliminates the risk of mishandled or misplaced samples. 

The case for automated time\control

Sample backlog and turnaround time are the two largest issues facing forensic analysts, and are compounded by searching for misplaced or mislabeled samples, searching multiple sample storage locations, or having to re-test a challenged sample. Time also mounts during manual recordkeeping and routine sample and documentation audits, and pulls attention away from sample results analysis and interpretation.

Efficient, hands-free storage and retrieval of DNA and small biological samples is enabled through automated sample storage systems; even for samples requiring decades-long storage. When the automated sample system is integrated into the forensic lab’s LIMS, all information and activity is automatically documented, so users don’t have to spend time manually logging or inputting data. Report generation time is also reduced compared to manual methods, as the traceable digital audit trail of each sample and performance of the storage system can be downloaded and output for court reports or emailed to others involved in the case. Additionally, compiling sample storage data over time may also yield trends that can help to further improve overall forensic laboratory efficiencies.

Increased crime, longer sample storage timeframes, and stronger dependence on forensic lab services place heightened demands on forensic lab workflows. Therefore, it’s important to recognize that by automating tasks such as sample storage and retrieval while documenting and maintaining control of sample integrity and chain of custody, labs can meet these elevated demands without the far-reaching risks associated with manual methods.

1.    The Biological Evidence Preservation Handbook: Best Practices for Evidence Handlers; NISTIR 7928; U.S. Department of Commerce, National Institute of Standards and Technology, U.S. Government Publishing Office: Washington, DC, 2013; pp. 17.
2.    Shao, W.; Khin, S.; Kopp, WC. Characterization of effect of repeated freeze and thaw cycles on stability of genomic DNA using pulsed field gel electrophoresis. Biopreserv Biobank. 2012, 10(1), 4-11.

Johann van Niekerk has 16 years of experience as a forensic scientist, with six years focusing on automated processing of evidence material. In his current role as Senior Sales Engineer at Hamilton Storage GmbH, he focuses on automated sample storage and retrieval solutions for biobanking, compound storage and forensic applications.