Since the day that Greg Harlen was admitted to Springfield Hospital in mid-April, his relatives and Delaware County authorities have been trying to determine how he broke both of his hips.

Was Harlen, who had Down syndrome, assaulted by a caregiver at the Cardinal Krol Center, the home for mentally handicapped men where he had lived for 43 years?

Did he fall?

Was the trauma somehow self-inflicted?

Harlen, 52, died in May of complications from his injuries. His family suspects that he was beaten inside the Philadelphia Archdiocese-run center in Marple Township. They've posted a $15,000 reward for tips that they hope will lead investigators to whoever may have assaulted him.

But police say that they don't have sufficient evidence to support the theory that he was assaulted - or any provable theory for that matter - and Harlen was unable to speak after he was hospitalized.

Now, it's looking as if his death could remain a mystery.

Last week, Harlen's family finally received a long-awaited medical examiner's report that they'd hoped would shed some light on how he was injured. Instead, the report stated that his manner of death "could not be determined."

"My brother could never tell them what happened," said Harlen's sister, Sheila Phelan. "I think there's a good chance we may never know, I really do."

Marple Township Police Chief Thomas Murray said yesterday that the inconclusive autopsy had essentially halted the investigation.

"Not that it's a closed case, but it is not being actively investigated unless we develop some additional information that would lead us someplace," he said.

Murray said that detectives had uncovered no evidence "that leads us to the conclusion that any wrongdoing took place." Nor have they been able to determine, after interviewing and reinterviewing employees at the Cardinal Krol Center, how he was injured.

"I wouldn't venture any kind of guess as to what could have happened," he said. "A lot of things can happen. What causes those injuries I don't know. If the coroner can't give us anything conclusive, who am I to say we have an idea what happened? We really don't. It's a tragic event."

The 131-bed Cardinal Krol Center has repeatedly been cited by state Health Department inspectors in recent years for violations. Its certificate of compliance was temporarily revoked twice over the past year due to "serious substandard conditions," but the center has since corrected those issues.

Philadelphia's Department of Behavioral Health and Mental Retardation Services determined that employees should have gotten Harlen medical attention sooner, but it is unclear whether the delay played any role in his death. The department has had Harlen's case file since he moved into the center from Northeast Philadelphia.

Sheila Phelan said yesterday that she remains hopeful that someone will come forward with information about how her brother received his injuries.

Otherwise, she said, "It's a dead end."

Anyone with information about the cause of Harlen's injuries should call the Citizens Crime Commission at 215-546- TIPS (8477).