What is a common procedure for collecting hair evidence at a crime scene?

Collecting hair evidence using tweezers or lifts to package them in an envelope is considered a best practice in forensic science. This method ensures the integrity of the hair samples while minimizing contamination or loss of evidence. Tweezers or specialized lifts allow for precise collection, especially in crime scenes where hair may be found amidst other debris, such as fibers or dirt. Once collected, placing the samples in an envelope helps preserve them, keeps them secure during transport, and prevents damage. This procedure follows forensic protocols that aim for preservation and chain of custody, which are essential for the credibility of evidence in legal proceedings.

In contrast, using a vacuum cleaner might inadvertently mix the hair with other materials and compromise its integrity. Collecting hair by hand risks damaging the strands or altering essential characteristics, and cutting hair samples directly from a person's scalp is not ethical or legal without proper consent, and it typically requires a different procedural context such as an official investigation.