What is essential to prevent when handling DNA evidence?

The focus when handling DNA evidence is to ensure the integrity of the samples, making it crucial to prevent contamination. This is vital because contamination can lead to the introduction of foreign DNA, which affects the validity of the evidence and the outcomes of the investigation. Maintaining a clean environment and using proper techniques when collecting, transporting, and analyzing DNA samples helps ensure that the evidence collected is true to the original source.

While preventing contamination is a central concern, other aspects mentioned in the choices also play important roles, such as controlling sample contamination, isolating samples to avoid cross-contamination, and regulating storage temperatures to preserve the evidence's integrity. However, the direct emphasis on contamination control reflects its primary importance in forensic protocols for handling DNA evidence.