Forensics & Evidence

How TEPD turns a crime scene into a case — casings, blood, prints and GPS trackers, all weighed into the file that decides your charge.

Every crime leaves something behind. Shell casings, blood, fingerprints, a scared witness — TEPD’s forensic toolkit is how officers turn a messy scene into an evidence file that stands up when a case goes to charge. This article covers how the physical side of an investigation works. For the digital side — CCTV, facial recognition, ANPR — see Investigations & CCTV. For what happens once you’re actually cuffed, see Arrest, Court & Prison.

Crime Scenes & Cordons

When an officer drops a cordon at a scene, it shows up as a coloured marker and map blip — red for unsecured, blue for secured. This matters more than it looks: anything collected from an unsecured scene is automatically weaker evidence, so the first job on arrival is usually to lock it down before touching anything.

A cordon left unattended for too long releases and purges itself — scenes aren’t meant to sit forever, and neither is the evidence inside them.

Securing the scene first isn’t box-ticking — every trace collected before you secure it comes in materially weaker.

Collecting Physical Evidence

Standing inside an active scene, an officer can examine the area to scan for anything nearby — casings, blood pools, bodies, and any latent contact points left on surfaces. Picking an item plays out a short bagging animation before it’s logged as a formal exhibit under a case file.

A few evidence types need a specific approach:

• Fingerprints are lifted from a vehicle by dusting it, provided the officer is carrying a dusting kit. A lifted print either matches a known identity outright, or files as an unidentified marker that can resolve later (see Cold Hits below). Prints get weaker the longer they’ve sat unprocessed, so an old print is a shakier match than a fresh one.
• Gunshot residue is picked up by swabbing a suspect at close range with a swab kit. It only reads positive if that person genuinely fired a weapon recently — the window doesn’t last long, so a swab minutes after the fact can already come back clean.
• Shell casings and blood are collected the same way as any other trace found during a scene examine.

None of this evidence lasts indefinitely. Casings, blood, and general scene traces all purge on a retention timer if nobody comes to collect them — turn up late enough and the scene really is clean.

The Forensic Lab Queue

DNA, blood, fingerprint, and GSR exhibits don’t count at full weight the moment they’re bagged — they file as pending and only score a fraction of their real value until they’ve gone through the lab. An officer holding the CID ticket can process the whole queue instantly from the lab desk; without one, everything still clears automatically, just on a delay.

This is why serious cases benefit from a detective’s attention early — the sooner biological and print evidence is processed, the sooner it counts at full weight.

Evidence Lockers & Chain of Custody

Seized property and bagged exhibits are held at a dedicated evidence locker — a shared stash any on-duty officer can access, not restricted per case. Every exhibit carries a chain-of-custody record: who collected it, when, and under what conditions. An exhibit that’s been tampered with, or whose chain is broken, scores nothing towards a case’s strength — it still shows up in the case file and can be challenged, it just carries no weight.

GPS Trackers

An officer carrying a tracker item can plant one on a vehicle at close range. From that point, the vehicle’s live position relays back as a personal map blip — visible only to the officer who planted it, and only for a limited window before the tracker stops relaying. When it matters, that live position can be locked in as a formal GPS exhibit on the case, turning a live tracking dot into evidence that survives the tracker’s own expiry.

Comms Warrants

Pulling a suspect’s call and message history isn’t something an officer can just request — it needs an active warrant raised against that person through TEPD’s case system. With a live warrant in place, a summarised history files into the case as its own exhibit, stamped with the warrant reference. There’s no back door here; without a warrant, this evidence simply isn’t available.

Case Strength & Charging Decisions

Every exhibit contributes weight to a case’s overall strength score, which is what drives whether a case supports a full charge, a reduced one, or no further action. Some exhibit types carry serious weight — DNA and bodies sit near the top — while things like a single document or an ANPR hit contribute much less on their own. Independent evidence pointing at the same suspect from different angles compounds: a second unrelated exhibit tying back to the same person adds extra weight beyond what either piece would carry alone, so a case built on several corroborating threads is a lot stronger than one resting on a single exhibit.

Cold Hits

Fingerprints and DNA aren’t only useful in the moment. Every time someone is formally booked into custody, their biometric details get enrolled. If an old, unresolved print or DNA marker from a past scene matches that person, it links retroactively — and can raise an arrest warrant on its own, days or weeks after the original crime, without anyone re-opening the case.

Leaving Less Behind

Wiping surfaces, bleaching blood, sweeping up casings, torching a vehicle, or simply working masked and gloved all reduce what TEPD has to work with — but every one of those actions carries its own tell, and none of them are guaranteed to be clean. The full counterplay picture, including what still gets through, is covered in Evading the Law. For how all of this fits into the wider risk of a life of crime, see Crime & Consequences.