On television, a bloody shirt goes from the crime scene to a DNA match somewhere between two commercial breaks. Real evidence often spends its first days doing something much less dramatic: drying. A garment soaked in blood cannot go straight into a box and onto a shelf, and the reason is biological, not bureaucratic.
The clearest description of that step is in The Biological Evidence Preservation Handbook, published in 2013 by the U.S. National Institute of Standards and Technology and written by its Technical Working Group on Biological Evidence Preservation. The advice is blunt. Apart from items that have to stay liquid, such as blood-draw tubes, evidence that arrives wet should be dried before it is stored, and drying a blood-soaked garment should be the first task of whoever handles it.
Why wet evidence works against itself
A damp shirt is a good home for bacteria and mold, and they feed on the same biological material an analyst will need later. The handbook warns that if wet evidence is not air-dried correctly, there is a high probability that bacterial growth will destroy the biological material, which could rule out a DNA result altogether.
That is also the trouble with the plastic evidence bag from the movies. Plastic traps moisture, so the handbook allows it only as a stopgap, with two exceptions: bags that contain a desiccant, and breathable Tyvek bags for damp items and swabs. When an item has to wait in its wet state, the recommendation is an impermeable container such as a metal can or a glass jar, kept in a refrigerator at 2°C to 8°C (about 35°F to 46°F) and out of direct sunlight until it can be dried or sent to the lab.
Lockers, shower stalls and tiled rooms
Not every agency handles enough wet evidence to justify special equipment, and the handbook is practical about that. Its low-tech options include a metal locker labeled for biohazards, a room set aside for the job, and, for departments with little money, a prefabricated fiberglass shower enclosure raised on a wooden frame so the runoff can drain. A hose on a nearby faucet makes it easy to wash the whole thing down afterward.
The small details are where a case gets protected. Wet garments hang with sterilized paper beneath and between them. That paper is packaged separately and submitted with the garment, because whatever fell off while it dried may be trace evidence too. The drying area should stay out of direct sunlight, between 15.5°C and 24°C (60°F to 75°F), with relative humidity no higher than 60 percent. A room dedicated to drying should be under negative pressure, with 12 to 15 air changes per hour vented to the outside of the building.
What a drying cabinet changes
For larger departments that dry evidence every day, the handbook names a commercially made evidence drying cabinet as one of the most acceptable methods. The item is secured inside while air circulates through a HEPA filter that pulls out airborne particles. One line in that section would make a good plot twist: the HEPA filter may become evidence as well, since it holds whatever the air carried off the item.
A cabinet also protects the people working around the evidence. Blood-soaked clothing can carry blood-borne pathogens, and an open locker in a corridor does nothing to keep them away from staff. Manufacturers design for both problems at once. TopAir Systems, for instance, builds its evidence drying cabinet from polypropylene, with pre-filtered intake air, HEPA and carbon filtration on the exhaust, a UV lamp that disinfects the interior between sessions, a display for the humidity and temperature inside, and a draining basin at the bottom. Widths run from about 30 inches to 96 inches, which is roughly the difference between drying a single shirt and hanging a full set of bedding.
The rules nobody films
Some of the handbook reads like housekeeping, and that is deliberate. Paper goes under every item, whatever kind of cabinet or locker is used. Hangers are not reused. Surfaces are decontaminated with a freshly made 10 percent bleach solution, and evidence managers are asked to write down who cleans the drying area, how it is cleaned, and how long those records are kept.
Once an item is dry, it goes into its own new paper bag or another breathable container, sealed and marked as biohazardous material. Every one of those steps can be questioned in court years later, and a gap in the record is an easy target.
On screen, the shirt goes from the crime scene to a glowing match on a monitor. Off screen, it hangs in a locker, a shower stall or a cabinet first, over a sheet of paper that gets bagged up and kept with it.
Amanda Lancaster is a PR manager who works with 1resumewritingservice. She is also known as a content creator. Amanda has been providing resume writing services since 2014.
