Cut the Clutter: Reimagining Evidence Collection to Improve Downstream Processing

 Cut the Clutter: Reimagining Evidence Collection to Improve Downstream Processing

Welcome to Forensic’s first (of four) installment of  “Dr. Miller's Unfiltered Tips.” This column is authored by Dr. Kevin Miller, Senior Market Segment Leader for Government and Regulated Laboratories at Hamilton Company in Reno, NV. After earning a Ph.D. in Molecular Anthropology from the University of Cambridge, Dr. Miller actively engaged in promoting, researching, and furthering forensic science advances, and remains committed to this endeavor today. In his words, "I am a forensic geneticist who, like most forensic folks my age, fell into the field from somewhere else (I was digging up Viking remains in the Northern Isles of Scotland, but that is a completely different story) and stayed … at least until I brought automated liquid handling to my laboratory. Now I work with automation engineers, and try to make sense their world for the people in mine. I’ve picked up a lot of tips, and given away a few. Sometimes useful. Always unfiltered."

At a crime scene, a natural first inclination may be to collect and swab as many items as possible. Body fluids, hair, items that may have been worn, touched, or splattered upon – they’re all fair game when looking for DNA that can help to identify an assailant.

All collected evidence, and every swab taken of those items, has to be sealed in a primary container that is sealed inside a secondary container. Place, seal, label, repeat.

And what is the result?

Swabs. Swabs in boxes. Swabs in boxes in envelopes. Swabs in boxes in envelopes in boxes. Cigarette butts. Cigarette butts in paper bags. Cigarette butts in paper bags in bags with other bags…in a box…or a bag. I once had a bloodstain shipped to me. It was in the trunk of a car that was placed in a wooden box and delivered on a pallet. My mail carrier still talks about it.

In addition to packaging, the risk of documentation errors by harried crime scene or law enforcement personnel working in the midst of potentially emotionally charged situations cannot be overlooked. Even without errors on their part, some of these folks have penmanship rivaling that of a medical doctor, leading to translation errors by lab analysts.

Is that a “P” or a “D”? An “8” or a “B”?

This multitude of samples in progressively larger containers takes up valuable space in evidence storage areas. As samples are pulled for testing, analysts peel back all the packaging layers – unseal, remove, repeat – to get to the actual sample and then immediately reverse the process – place, reseal, relabel, repeat – so that the collection can go back on the shelf.

All of those samples, even if they are redundant or devoid of DNA, have to be gathered from storage, prepared, tested, and returned to storage which, of course, leads to never-welcome backlog and turnaround roadblocks.

There’s got to be a simpler way, right?

Well, of course there is!

Did I just hear a collective sigh of relief? Feels good, right? You go ahead and keep up with the deep, cleansing breaths as we dive into the details together.

This new path is a reimagination of evidence collection, processing, and storage. Throw out traditional evidence collection kits, each with different configurations and contents specific to an offense type (e.g. sexual assault, property crime, etc.). Instead, standardize on a common, uniform, and automation-friendly collection tube.

At a crime scene, this specialized tube format encourages evidence collectors to be quite intentional about the evidence that they collect instead of trying to collect everything. Swab heads, small pieces of fabric, cigarette butts, and other biological evidence samples may be placed into the tube and safely transported in the tube’s original, writable packaging instead of a series of progressively larger containers. A unique 2D barcode embedded into the tube creates an automatic and permanent chain of custody from the time of collection throughout the sample’s life cycle, including potential decades of property room storage.

In storage, fewer packaging layers frees up valuable storage space and also reduces documentation errors, contamination risk, potential for loss, and the amount of time spent unsealing and resealing each layer every time the sample is accessed.

In the forensic laboratory, the utility and unique nature of this novel tube really stands out. For starters, it’s not just a 2D barcoded tube, it’s actually a tube within a tube – a spin basket! The tube may be placed directly onto an automated liquid handling workstation specially designed for use with the tube. One iteration of this workstation processes up to 48 mixed samples from sexual assault cases and is appropriate for use with multiple processing methods, including traditional differential extraction, affinity capture of unique sperm proteins, nuclease-based digestion, and matrix-derived separation. Another iteration enables hands-free parallel batching of up to 96 biological samples collected from other types of violent crime at once.

The automated workstation guides analysts through setup and automatically calculates reagent volumes, then performs tasks such as automatically capping and decapping each evidence tube, reagent additions, washing, and moving samples around the deck for centrifugation, incubation, and shaking steps. Before the method even starts, each outer tube’s 2D barcode is automatically scanned to either accession the evidence, if you’re smaller lab, or to continue the chain of custody in labs that have dedicated evidence control units, and the samples are independently verified and correlated with the item number, case file, and assigned analyst.

During processing, specialized channels lift and lock the inner tube into a spin basket position without the need for manual intervention so that the outer tube can receive cleared sample lysate for downstream processing. When used for sexual assault sample processing, the sperm containing pellet is retained in the inner tube and may be resuspended as the sperm fraction for downstream processing.

In addition to maintaining an unbroken chain of custody, the automated method reduces time spent performing low value activities and verifying the work of others. The system may be integrated with a LIMS for automatic evidence accessioning and/or worklist generation, and once the workflow is complete, a standardized report including sample type, location and action may be generated for inclusion in a case file report.

One small, novel tube, along with an automated workstation, can cut through the clutter of DNA evidence collection through processing so that everyone involved in the case can move forward with a high degree of confidence in results that support the investigation.

The novel sample collection tube and automated instrumentation help to eliminate the frequency of these human errors along the evidence sample cycle, from sample collection through processing and documentation. As a result of fewer human-based errors during sample collection and processing, everyone involved in the case can move forward with a high degree of confidence in results that support the investigation.

More of Dr. Miller's Unfiltered Tips will be published the third Friday of April, July and October.