Customer loyalty cards and crime-fighting

An interesting example of how data gained through the use of a customer loyalty card can be quite problematic for the individual customer can be found at slashdot today:

“Tukwila, Washington firefighter, Philip Scott Lyons found out the hard way that supermarket loyalty cards come with a huge price. Lyons was arrested last August and charged with attempted arson. Police alleged at the time that Lyons tried to set fire to his own house while his wife and children were inside. According to KOMO-TV and the Seattle Times, a major piece of evidence used against Lyons in his arrest was the record of his supermarket purchases that he made with his Safeway Club Card. Police investigators had discovered that his Club Card was used to buy fire starters of the same type used in the arson attempt. For Lyons, the story did have a happy ending. All charges were dropped against him in January 2005 because another person stepped forward saying he or she set the fire and not Lyons.”

What if the person who really committed the arson had not had the decency to step forward? What if the crime in question had been a murder where the actual murderer might face the death penalty if he or she came forward? The above story demonstrates the problem that “objective” traces such as data from customer records are taken to be sufficient when investigating a crime, and that alternatives may then no longer be pursued.

Update: A similar story, albeit not about crime, where a customer loyalty card was used to the clear disadvantage of the owner, can be found here.