However, ISPs have widely varying policies for storing such data, with some deleting it in a manner of days and others retaining it for months, he said. By making it compulsory for them to store usage data for specific lengths of time, law enforcement authorities are assured of getting access to the data when they need it, he said.

In his testimony, Weinstein admitted that a data retention policy on the industry raised valid privacy concerns. However, such concerns need to be addressed and balanced against the need for law enforcement to have access to the data, he said. "Denying law enforcement that evidence prevents law enforcement from identifying those who victimize others online," Weinstein said.

John Douglas, chief of police in Overland Park, Kansas and a representative of the International Association of Chiefs of Police, .

"Clearly, preserving digital evidence is crucial in any modern-day criminal investigation," Douglas said in his prepared testimony for the House subcommittee. On occasion, law enforcement has been able to use existing legal processes to get ISPs to preserve data in connection with specific investigations, he said.

However, because of widely varying data retention policies, sometimes law enforcement requests for protecting data are made too late. "There are cases where we are not able to work quickly enough -- mostly because a 'lead' is discovered after the logs have expired or we are unaware of the specific service provider's protocols concerning data retention time periods," Douglas said.