What is one important characteristic of blood and DNA as evidence?

The correct choice emphasizes that blood and DNA as evidence remain unchanged over time, which is a crucial characteristic in forensic science. This stability allows forensic experts to analyze biological samples long after they have been collected, providing reliable and consistent results that can be used in legal contexts.

Blood and DNA contain unique genetic information that does not change, barring any external interventions such as contamination or degradation due to improper storage conditions. This characteristic is vital for establishing links between individuals and crime scenes, as well as maintaining the integrity of the evidence throughout the investigative and judicial processes.

The other options highlight concerns that do not hold true for the longevity and reliability of blood and DNA as evidence in forensic investigations. For example, while it is important to handle evidence carefully, they are not easily lost during transportation when proper protocols are followed, and there is no strict 24-hour time limit for collection that universally applies to all cases. Therefore, the stability and unchanging nature of blood and DNA make them powerful tools in the pursuit of justice.