How long can liquid blood be preserved at a crime scene before it alters findings?

The preservation of liquid blood at a crime scene is critical for the integrity of forensic analysis. Typically, liquid blood can begin to show significant changes relatively quickly due to environmental factors, such as temperature and exposure to air. When considering how long blood can be preserved without altering findings, two hours is generally considered the maximum allowable time before degradation processes start undermining the sample's reliability.

After this period, the blood may start to clot or undergo other biochemical changes, which can affect the tests conducted later. Forensic experts often advise prompt collection and analysis within a short window to ensure the sample retains its original properties and provides reliable evidence for investigations.