A detective who launched an initial and "flawed" investigation into serial killer Harold Shipman confessed he was defeated by the unprecedented nature of the case.

Detective Inspector David Smith said his hands were tied by the magnitude of the allegations and the need to conduct the inquiry with maximum discretion without alerting Shipman.

There were no guidelines on dealing with the unusual case, and the inquiry was hampered by complex medical jargon and patient confidentiality, he said.

After a "discreet" and "confidential" four-week-long investigation the case was dropped in March 1998 - after which Shipman went on to claim more victims.

It seemed the type of inquiry that was so incredulous

Detective Inspector David Smith

The detective inspector told the Shipman Inquiry at Manchester Town Hall he first was alerted to suspicions against Shipman by Manchester coroner John Pollard.

"He had concerns that Shipman was killing his patients," said Mr Smith.

An investigation was then launched to collate any evidence "to substantiate the concerns".

Complex case

Mr Smith told the inquiry his inexperience in any similar case left him at a loss as to where to even start collating evidence.

"It was something I had never experienced before and it was start at the beginning and follow on from there," he said.

Dame Janet Smith is heading the inquiry

Initial steps involved obtaining death certificates and speaking to the doctor who originally raised the allegations about Shipman's crimes.

Mr Smith said he needed to trace medical records, death certificates and obtain more information.

"I didn't really know where to go for this information," he said.

He said he was faced with a brick wall with issues of patient confidentiality and being told not to speak to Shipman.

"It seemed the type of inquiry that was so incredulous that if people became aware of it, it would become known to others," said Mr Smith, adding that he feared it could be "leaked".

Having finally obtained the death certificates of 20 of Shipman's patients, he struggled to understand the medical terminology used.

"I did not know at that stage what the technical terms referred to," he added.

Obtaining information

The inquiry has heard the initial investigation by Greater Manchester Police was "flawed".

In the following five months before his arrest, Shipman killed Winifred Mellor, 73, Joan Melia, 73, and Kathleen Grundy, 81.

Shipman was eventually convicted of killing 15 elderly women but is suspected of killing hundreds more with fatal injections.

Earlier this month, Greater Manchester Police offered its "regrets" to the families of Shipman's victims, adding that the "strategic management" of the case had been "flawed".

The investigation was "terminated prematurely" in April 1998, said Michael Shorrock QC, for GMP.

Shipman is currently serving life at Frankland Jail, Co Durham, after being convicted of 15 counts of murder at Preston Crown Court in January 2000.

'Strangely passive'

The inquiry also heard that Detective Inspector Smith interviewed Dr Linda Reynolds, the first person to raise concerns that Shipman was killing his patients.

She worked in a practice close to his and had noticed the high death rate among his female elderly patients.

Caroline Swift QC, counsel for the inquiry, accused the police officer of adopting a "strangely passive" attitude while interviewing Dr Reynolds.

Mr Smith said he "probably" had not asked the right questions.

He added that when the initial inquiry into Shipman's crimes had concluded, "there was nothing to say that Shipman was killing his patients".

The Shipman Inquiry has been adjourned and resumes on Tuesday.