The findings will then go to the police commissioner, who has the final say.
"We don't know what happened," Sadler said. "Was there a delay getting an arrest warrant to pursue additional information?"
Lewis, 21, an Olney High School dropout, is in jail, charged with the slaying of Cassidy, who was shot in the head Oct. 31 when he interrupted a robbery in progress that morning at a Dunkin' Donuts in West Oak Lane. Cassidy died the next day.
An employee of Oasis Pizza in Feltonville positively identified Lewis as a regular customer who showed up Oct. 20 with a gun demanding cash. He fled with $150. Despite the identification, no arrest warrant was obtained.
Officials said the internal investigation would focus on several questions:
Did the detective follow protocol in gathering information and pursuing it, or was the detective neglectful when an arrest warrant was not obtained?
Was the detective still investigating the case and looking for more evidence to secure a warrant? Was she assigned another job that took precedence in the busy East Detective Division, which covers some of the city's most crime-ridden neighborhoods?
The question no one can answer is whether Cassidy's death could have been prevented had a warrant been obtained and Lewis arrested, police officials said yesterday.
The name of the detective, who has been on the force for more than 20 years, has been withheld because of the pending investigation. Several people who know her said she was distraught about Cassidy's death.
Many in the police community said the case was troubling on several levels as police try to heal from the loss of Cassidy, a popular patrol officer from the 35th District, while they cope with an investigation of one of their own.
