Dr. Harold Shipman, the World's Most Prolific Serial Killer

Because of the nature of the Shipman case, it may never be possible to document every murder he committed.

A clinical audit commissioned by the Department of Health estimates his responsibility for the deaths of at least 236 patients over a 24-year period.

This audit, by Professor Richard Baker of the University of Leicester, examined the number and pattern of deaths in Harold Shipman's practice.   It then compared them with those of other practitioners.   Significant differences appeared, notably that the rates of death in elderly patients were disproportionately higher.

Other variations appeared; deaths were often clustered at certain times of the day, patients' records and previous symptoms mismatched, and Shipman was usually in attendance.

Professor Liam Donaldson, Chief Medical Officer for the Department of Health, wrote that these factors "must now be investigated by the proper legal authorities."

Detective Chief Superintendent Bernard Postles, who headed the original investigations, said of the report 'many of its conclusions accord with our own findings to date.' He noted the death toll estimated in the audit was "broadly in keeping with the number of deaths investigated by Greater Manchester Police during the course of the investigation."

Even so, the final numbers are anyone's guess — Coroner John Pollard once speculated "we might be looking at 1000."

But whatever the final count, there is no immediate plan to try the killer on future findings — nor would it serve much purpose because he's already serving 15 concurrent life sentences.

Instead, other cases are being investigated as they come to light, with coroners' verdicts of unlawful killing continuing to mount.   As they do, the question most asked is this:   Why wasn't he stopped sooner?