What practice is essential to ensuring DNA evidence remains reliable from collection to storage?

• A. Using sterile tools and proper packaging with chain of custody.
• B. Leaving evidence exposed to air to dry naturally.
• C. Mixing evidence from different cases.
• D. Freezing all evidence at absolute zero.

Answer: (A)

Preserving DNA evidence from collection through storage hinges on preventing contamination and maintaining a clear record of handling. Using sterile tools and proper packaging prevents introducing foreign DNA and keeps the sample intact, while tamper-evident packaging protects against tampering and degradation. The chain of custody documents every person who handles the evidence, when, and where, providing a traceable history that the tested material came from the original case and has not been altered.

Other options undermine reliability: letting evidence dry in the air can introduce environmental contaminants and degrade the DNA; mixing materials from different cases risks cross-contamination and complicates analysis; and freezing at absolute zero is not feasible or appropriate for evidence storage. In practice, evidence is kept under controlled conditions with careful handling to ensure the DNA results are trustworthy and admissible.