San Diego, CA, February 18, 2002
A healthy young Marine, Sgt. Todd Sommer, keels over unexpectedly. His wife Cynthia calls 911.
NCIS, the Naval Criminal Investigative Service, discovers arsenic in Todd Sommer's tissues and charges his wife with murder. She is convicted and sentenced to 25 years to life in prison. But when later toxicology testing doesn't confirm the earlier finding, her conviction is overturned and she is released.
TO FIND OUT WHAT HAPPENS NEXT:
Watch "An Invisible Enemy" Saturday, June 27 At 10 p.m. ET/PT On 48 Hours | Mystery
© 2009 CBS Interactive Inc. All Rights Reserved.