Denver's outgoing Independent Monitor, Richard Rosenthal, released a scathing report on police discipline today, saying that the department is unable to investigate itself.

Members of the Internal Affairs Bureau, charged with investigating police misconduct, drag their feet in examining the incidents, fail to ask important questions, and show bias in favor of the officers they investigate, Rosenthal said.

Among his conclusions in the fourth quarter report was that "bias on the part of Internal Affairs Bureau investigators and supervisors has been documented in many cases over the past year."

"It is the opinion of the Monitor that these cases evidence substantial problems in the way the Denver Police Department is currently policing itself," Rosenthal wrote.

In one case, an investigator "attempted to explain away the officer's conduct to the complainant and witnesses and also asked leading and suggestive questions evidencing bias in favor of the subject officer," the report said.

In another case, Rosenthal wrote that the investigator provided both the officer under investigation and witnesses with inaccurate information.

In that same case, the investigating officers failed to interview all necessary witnesses before interviewing the subject officer.

According to Rosenthal, "This action resulted in inaccurate information being provided to the subject officer during his interview and required that a reinterview ... be conducted months later, which potentially impacted his ability to recollect."

In that case, investigators also "exhibited significant bias in favor of the subject officer."

In another case, IA refused to ask permission to obtain cell tower records from members of a family who claimed that an officer left them stranded after ordering one of them not to drive because of a lack of insurance. The family members claimed they were stranded for 45 minutes before the officer's supervisor gave them permission to drive home. The officer claimed "multiple times that the complainants had, in fact, driven away within 5-10 minutes," the report said.

The cell tower records would likely have established where they were located during the 45-minute period. "At any point in time during the command review process, the department could have requested that the cell tower information be obtained," Rosenthal wrote.

As a result, a complaint of committing a deceptive act was not sustained, although there had been no conclusive proof about what really happened.

Rosenthal, who came to Denver in 2005 from Portland, Ore., where he had initiated an independent monitor's office, is leaving the position at the end of the week to create and head a new independent investigations office in British Columbia.