Evidence tape is a tamper-evident seal used to secure physical evidence so that any unauthorized access becomes immediately visible. It protects everything from blood samples to firearms from the moment they’re collected at a crime scene until they’re presented in court. Without it, there’s no reliable way to prove that evidence hasn’t been opened, contaminated, or swapped out along the way.
How Evidence Tape Reveals Tampering
Evidence tape works through self-destructing properties that make secret removal virtually impossible. Most forensic evidence tape is “frangible,” meaning it tears apart rather than peeling off cleanly. Serrations built into the tape make it even more sensitive to tearing. If someone tries to lift the tape, it shreds, leaving obvious damage that can’t be hidden or reversed.
Many evidence tapes also use a chemical trick: when removed, the adhesive leaves behind a residue on the surface that spells out “OPENED” or “VOID” in repeating text. Even if someone tried to replace the tape with a fresh piece, the message printed on the package underneath would give them away. Some tapes feature diagonal lines printed across them, so if the tape were cut or punctured and someone tried to realign the pieces, the mismatched pattern would be immediately noticeable.
Why It Matters for Court
Evidence tape exists primarily to maintain the chain of custody, the documented trail showing every person who handled a piece of evidence and confirming it remained secure between each handoff. The National Institute of Justice requires that every person who touches an evidence item sign for its possession, and that items be packaged so their evidentiary value isn’t destroyed.
At trial, defense attorneys routinely challenge whether evidence was handled properly. If there’s any indication of missing items, mislabeling, contamination, or breaks in the chain of custody, a judge can rule evidence inadmissible. Evidence tape provides the physical proof that a sealed package stayed sealed. A container with intact, unbroken tape and matching initials tells the court that no one accessed its contents between collection and analysis.
How Evidence Tape Is Applied
Applying evidence tape follows a specific protocol that goes beyond just sticking tape on a bag. According to guidelines used by agencies like the San Diego County Sheriff’s Department, every seal must include the sealer’s initials and the date, written in permanent marker across the tape and onto the package itself. This detail is critical: because the writing spans two surfaces (the tape and the container), removing and replacing the tape would break the continuity of the handwriting, creating another layer of tamper detection.
For paper bags and manila envelopes, the opening is folded over and sealed along its entire length with a piece of evidence tape longer than the width of the opening. Boxes get tape across every seam that could be opened. Every single piece of tape on a package gets its own initials and date.
When evidence needs to be reopened for lab testing, the original seal is never removed. Instead, a new opening is made, and once the item is returned, the new opening gets its own fresh piece of evidence tape with a new set of initials and a new date. The previous markings stay visible, creating a visible history of every time the package was accessed.
Types of Evidence Tape and Seals
The most recognizable type is bright red pressure-sensitive tape with bold black repeating text identifying the contents as evidence. This coloring serves a dual purpose: it marks the item as evidence at a glance, and any cuts or tears show up clearly against the vivid background. Standard forensic tape like the commonly used Sawtooth brand runs about 1.25 inches wide on 108-foot rolls and fits in a dispenser box for easy use at crime scenes or in the lab.
Beyond standard tape, forensic suppliers offer several specialized options:
- Super-Stick integrity seals: Precut adhesive seals made from the same tamper-evident material, with permanent adhesive designed for surfaces where roll tape is impractical.
- Chain of custody labels: Larger adhesive labels (typically around 3.5 by 6 inches) that can be stuck to almost any surface and include printed fields for tracking who handled the item and when.
- Biohazard tape and labels: Used specifically for evidence containing body fluids, alerting anyone handling the package to take appropriate safety precautions.
- Trace evidence collection tape: A wider tape (around 3 inches) with water-soluble adhesive, used not for sealing but for lifting hair, fibers, and glass fragments from surfaces, similar to how fingerprint tape lifts dusted prints.
- Chain of custody tags: Printed on heavy paper stock with reinforced eyelets, these attach physically to items that can’t easily be bagged or wrapped.
What Happens When Evidence Tape Fails
If evidence tape is found broken, missing, or improperly applied, the consequences ripple through the entire case. A broken seal raises the question of whether the contents were altered, and the burden falls on the prosecution to prove they weren’t. In practice, compromised packaging gives defense attorneys grounds to argue for exclusion of that evidence. Even if the evidence itself is perfectly intact, the inability to prove it remained untouched can be enough to keep it out of the courtroom.
This is why agencies treat tape application as a nonnegotiable step rather than a formality. A forgotten set of initials, a date written only on the tape and not extending onto the package, or a seal that doesn’t cover the full width of an opening can all create vulnerabilities that get scrutinized months or years later during legal proceedings.