Crime scene tape is a long, thin material used to secure crime scenes by indicating that access will be denied to people who are not authorized to be in the area. The goal is to create a simple barrier to help prevent contamination of the crime scene while a crime is investigated. Many law enforcement professionals carry barrier tape in their kits, with their agencies ordering it from professional suppliers. People who are interested in this tape as a novelty item can often find it for sale at police surplus stores and novelty shops.
Classically, crime scene tape is bright yellow so that it will be highly visible, with black lettering and symbols, such as stripes. “Crime Scene: Do Not Cross” is a popular choice for lettering, and the tape may also reference the specific agency doing the investigating, such as police or a government agency concerned with national security and criminal investigations. As a barrier, the tape is primarily visual, since people can easily duck under it or step over it.
When law enforcement officials arrive at the scene of a crime, they may choose to put up this tape if they feel that sensitive evidence could be damaged or compromised. Murders and other serious crimes are usually grounds for breaking it out, and the tape may also be used in high-profile robberies and other cases. Once the tape is strung, officers may be posted in the area to ensure that only people with authorized identification are allowed to cross the barrier and enter the area.
It is extremely easy to destroy or contaminate evidence at the scene of a crime. Law enforcement officers are specially trained to navigate crime scenes and work with evidence to ensure that it is collected, handled, processed, and stored properly so that it can be used in investigation and presented as valid in court. Members of the general public do not have this training, and some may even have malicious intent to damage evidence if they can access the scene, making the barrier tape especially important.
In addition to being used to seal off sites under investigation, crime scene tape may also be installed over doorways, along with official seals to indicate that a room or building should not be entered without authorization. If someone does enter the room, he or she will break the seal, alerting law enforcement to the fact that the scene may have been compromised.