According to the statistics, 72 officers were killed by perpetrators in 2011.
The figure, one of the highest in nearly two decades, shows a 25-percent increase from 2010 and a 75-percent increase compared with 2008.
After several killings of officers last year, the FBI commissioned a study that found that, in many cases, the officers were trying to arrest or stop a suspect who had previously been arrested for a violent crime.
Some law enforcement officials believe that the techniques used by police may have put officers at greater risk by encouraging them to conduct more street stops and to confront suspects who may have guns.
The most risky situations are considered the ones where police officers pursue suspects, make traffic stops or arrest offenders.
AR/HJL/MA