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CHICAGO (CBS) — Chicago police claim the city’s murder rate went down more than 5 percent last year.

But did it really?

The 2 Investigators have reported for years about how the police department has killed crime on paper by misclassifying reports of robberies, rapes and murders.

It seemed like a deadly year in Chicago in 2010. But in the end, police bragged that murders were down from 460 in 2009 to 436 in 2010. Exiting Police Supt. Jody  Weis said it was the lowest homicide rate in 45 years.

But there’s unfinished business: dozens of so-called “uncleared death investigations,” which are yet to be classified as non-criminal cases or homicides.

Take the case of Jay Polhill. The body of the 20-year-old Columbia College student was found in the Little Calumet River naked from the waist down, according to police.

“He didn’t have his camera. He didn’t have his laptop. He didn’t have his wallet,” said Polhill’s friend, Taylor Streiff. “I believe he was murdered.”

Polhill’s autopsy report describes “extensive skull fractures” on both sides of his head and a broken neck bone. But the medical examiner’s office said the cause and manner of death was “undetermined.”

Unsatisfied, Polhill’s parents spent $15,000 on a private detective who they say helped them get the police and medical examiner to take another look. 

Polhill’s parents showed the autopsy report to a pathologist in another state. He told Zekman the documented head injuries don’t support an accident or suicide theory.

In fact, he said, “It really shouts out as an  assault.” 

Last October, the Polhills then met with the pathologist assigned to their son’s case in Cook County. A month later, after consulting with other pathologists in the medical examiner’s office, she amended her findings.

The amended cause of death is now  “drowning due to multiple injuries due to assault,” a homicide.

But five months later, Chicago police still list Polhill’s case as a death investigation.

Thomas Byrne, chief of detectives for the Chicago Police Department, says its cold case unit is now taking a fresh look at the case.

“It could turn into a homicide,” Byrne said.  

Asked if detectives feel pressured to help keep serious crime statistics down, Byrne replied, “Absolutely not.”

“There’s not a detective or a police officer out there that I know that would misrepresent a homicide as a death investigation,” he told Zekman.

Meanwhile, Polhill’s friends are afraid a killer may still be out there.

“If someone has the capacity to do that once, then they have the capacity to do that more than once,” Suzanne Pearman said.

Polhill’s parents anxiously await the outcome of the police investigation. Under the Freedom of Information Act, the 2 Investigators have asked for the case reports on dozens of other pending death investigations.