How many did Shipman kill?

Could Shipman have committed more murders?

The conviction of Dr Harold Shipman on 15 counts of murder brings to a close the trial of one of Britain's biggest serial killers.

But it does not represent the end of the story.

It can now be reported that those behind the investigation believe Shipman committed many more murders, beyond those for which he has been found guilty.

The police have investigated the deaths of 136 of his patients. Coroner John Pollard says: "It would not be unreasonable to say a figure of 150 would be a realistic, possible estimate."

The Crown Prosecution Service says it is ready to prosecute in 23 of those cases, if the families of the deceased permit it.

Earlier investigation

The end of the trial also means information which had been withheld from the jury for legal reasons can now be made public.

Firstly, there had been an earlier police inquiry into Shipman, six months before he was eventually caught. The investigation was dropped because of insufficient evidence and the GP went on to kill his final victims.

The Shipman Murders

Marie West:
6 March 1995

Irene Turner:
11 July 1996

Lizzie Adams:
28 February 1997

Jean Lilley:
25 April 1997

Ivy Lomas:
29 May 1997

Muriel Grimshaw:
14 July 1997

Marie Quinn:
24 November 1997

Kathleen Wagstaff:
9 December 1997

Bianka Pomfret:
10 December 1997

Norah Nuttall:
26 January 1998

Pamela Hillier:
9 February 1998

Maureen Ward:
18 February 1998

Winifred Mellor:
11 May 1998

Joan Melia:
12 June 1998

Kathleen Grundy:
24 June 1998

Secondly, that Shipman had a previous conviction dating back more than 20 years, for obtaining dangerous drugs.

Although that matter was referred to the General Medical Council in the mid-1970s, he was allowed to continue working as a GP.

Harold Shipman was a respected and trusted local doctor with more than 3,000 patients. They thought of him as someone who was caring, conscientious and hard-working.

But behind the façade, Shipman was driven by darker motives. His life was dominated by the need to kill, which he did time and again.

After each murder, he would go to extraordinary lengths to cover his tracks.

He was only caught following the death of Kathleen Grundy in June 1998, when her daughter, Angela Woodruff, suspected her mother's will had been forged.

It is the only known case in which Shipman attempted to benefit financially from killing.

Yet when detectives confronted him with proof that Mrs Grundy, 81, had died not from old age, as he had stated, but from a diamorphine overdose, Shipman tried to maintained the widower and charity worker, a pillar of respectability, had been a drug addict.

In fact, Shipman had already drawn police attention before Mrs Grundy's death.

Cremations caused concern

Three months earlier, doctors at a surgery in Hyde had raised concerns about the number of cremation certificates Shipman had been asking them to countersign.

An earlier police inquiry into Shipman was dropped

But a police inquiry was dropped because of lack of evidence.

But the evidence of a suspicious will sparked police back into action and a decision was made to exhume Mrs Grundy's body.

At the same time police decided to investigate the deaths of more than 130 of Shipman's other patients. They examined old medical records and questioned surviving relatives.

When the post mortem of Mrs Grundy revealed traces of morphine, Shipman was arrested. In his surgery, police discovered the typewriter on which her will had apparently been written.

Evidence of other murders began to emerge, along with a pattern of the type of victim he preferred.

All were women, either middle aged or elderly, mostly widows who lived alone.

Mrs Grundy's will sparked suspicion

In all but one of the murders Shipman visited them at home, mostly by appointment although sometimes unannounced. He injected them with morphine, presumably under some other pretext, because there was never any sign of a struggle.

After each death, Shipman would go to great lengths to avoid a post mortem, which he knew could implicate him.

When he started killing his patients is not known. But the way he obtained the diamorphine - the medical term for heroin - with which he murdered, was identical to the way in which he had earlier got hold of pethedine.

Now that Shipman's trial is over, police must decide what further action to take over the allegations of many more killings.

And the case itself has raised as many questions as it answered. For many the most fascinating is exactly why did he kill.

One explanation put forward by South Manchester coroner, John Pollard, who knew and worked with Shipman, is that he enjoyed the control.

Mr Pollard says: "I think the only valid possible explanation for it is that he simply enjoyed viewing the process of dying and enjoyed the feeling of control over life and death, literally over life and death."