APRI Highlights - Winter 2003

Heat and Blood Alcohol Levels

Nothing is worse than opening the trunk of a police cruiser and finding key evidence that has been accidentally left there for months. No one likes to discover a vial of the defendant’s blood from a DUI or vehicular homicide that has not been processed promptly. After all, it is the most important evidence in the case. What happens to blood that sits in cars, exposed to the harshest temperatures? How does heat affect the integrity of the blood test?

Defense attorneys will be the first to tell you that the heat causes blood alcohol concentration to rise, giving a higher reading than if the blood was refrigerated or promptly delivered to the lab. But, a new study says that’s not true.

P.L. Glover presented his pilot study, The Effect of Heat on Blood Samples Containing Alcohol, at the 2002 Conference of the International Association for Chemical Testing in Austin, Texas. Blood was drawn from donors and exposed to temperatures ranging from 62.6 degrees Fahrenheit to 116.24 degrees over 78 days. Temperatures were recorded every five minutes for the first 30 days. Some samples had a presence of alcohol ranging from .062 to .123 g/ml; other samples had no alcohol at all.

Here are the key findings:

• Blood samples exposed to high temperatures will not rise in blood/alcohol concentration.
  
  
• A decrease in blood/alcohol concentration occurs during the initial 72 hours followed by a continuous, but slight, decrease over the next 75 days.
  
  
• Refrigeration is recommended to prevent the blood/alcohol concentration from decreasing in the blood sample.
  

Therefore, another popular defense myth crumbles under scientific scrutiny: Blood/alcohol concentration actually decreases in the heat. If anything, every defendant whose blood sample was exposed to high temperatures has received a scientific benefit of a lower BAC result.

Of course, refrigeration is always the preferred and prudent method to maintain the evidence, but what about blood tests sent in to the lab by mail? In the future, the study will examine samples exposed to those conditions as well.

For further information, contact P.L. Glover, whose studies in this area continue at the Forensic Tests for Alcohol Branch, North Carolina Department of Health and Human Services, 1922 Mail Service Center, Raleigh, North Carolina, 27699-1922. If APRI can be helpful to you in any way, contact the National Traffic Law Center at (703) 549-4253 or trafficlaw@ndaa-apri.org.