Evidence is information or items presented to a court to prove or disprove facts of a case. This captures why the chosen option fits best: it points to something that is officially recognized and used in the legal process to determine what happened, under rules that govern relevance, reliability, and admissibility. In crime scene work, evidence can be physical items, documents, digital data, or witness testimony, but only when it can be evaluated and connected to the facts in question. A hunch, a presumption of guilt, or a rumor without verification are not evidence because they lack verifiable support and cannot establish facts in court.

Sampling exterior surfaces as soon as possible at the scene is essential to preserve the evidence in its original state. Exterior evidence is exposed to the environment and to handling, so delays can lead to loss, contamination, or alteration—from weathering, heat, moisture, wind, or contact with bystanders and investigators. Collecting at the scene keeps the evidence in its original context, which is crucial for accurate interpretation and for maintaining a solid chain of custody. Transporting the vehicle before sampling or waiting for a later inspection increases the risk that the trace material will be disturbed or destroyed, making lab comparisons unreliable. So, the best practice is to sample as soon as possible at the scene.

Transferring evidence between locations must be documented, keep a continuous chain of custody, and ensure the packaging stays sealed. This creates a traceable, verifiable record of every person who handles the item, along with when and where it moved, which is essential for integrity and admissibility in court. The seal on the packaging serves as a tamper-evident indicator, and it should be checked and re-sealed as needed during each transfer, with the transfer details logged in the chain of custody. Documentation is necessary even for small items because any gap in the trail can cast doubt on the evidence’s authenticity. Relying on supervisor approval alone or rushing transfers without proper records can undermine the evidence’s integrity.

Touch DNA is genetic material that is transferred to an object simply by a person touching it. It comes from tiny amounts of cells shed from the skin, along with other trace materials, and can remain on the surface long enough to be collected later. In crime scene work, investigators swab the surfaces that were touched to recover this DNA and possibly identify who touched the item, even when there’s no obvious biological evidence. The correct idea describes transfer of cells to a surface through contact, which is the essence of touch DNA. The other statements don’t fit: DNA isn’t limited to what’s found only on skin cells, it isn’t collected from air, and plant DNA isn’t relevant to human touch DNA.