Steve Wright has been convicted of murdering five women in Ipswich. But was he acting alone?
He may now be safely behind bars but, during his trial, the prosecution raised the possibility that Steve Wright may have been aided by an accomplice.
John Duffy (left) and David Mulcahy raped and murdered together
Prosecutor Peter Wright QC, suggested to the court that, when it came to the murders of Anneli Alderton and Annette Nicholls, evidence pointed to two possible criminals.
It would not be the first time a serial killer has had help.
The so-called "Hillside Strangler" killed 12 women in and around Los Angeles in the late 1970s. But the strangler turned out to be cousins Kenneth Bianchi and Angelo Buono, who were later jailed for life.
In 1988 the "Railway Rapist", John Duffy, was jailed for life for a series of murders and rapes near train stations in the London area. A decade later he told police about his accomplice, and in 1999 David Mulcahy was also given a life sentence.
The naked bodies of prostitutes Tania Nicol, Paula Clennell, Anneli Alderton, Annette Nicholls and Gemma Adams were found in and around Ipswich over a 10-day period in December 2006.
Prosecutor Mr Wright said the murders were "the work of the defendant, either alone or with the assistance of another".
The jury heard the bodies of victims Anneli Alderton and Annette Nicholls, may have been carried by two people into the thick woodland where they were discovered in December 2006.
The barrister said Miss Alderton's remains were "deposited some distance from the road".
He added: "There were no snag marks consistent with her naked form having been either dragged or carried through, past, under or over the low-lying branches and dense vegetation in the area.
"Of course, one possible explanation for this, we say, is that her naked body may have been carried by more than one individual."
On 8 December - the night Ms Nicholls went missing - a witness passing the spot where her body was later found reported seeing a dark Ford Mondeo, like the one owned by Wright, parked beside the road.
Next to it was a second car, which the witness thought was a Renault Clio. The witness said its interior lights were illuminated, the court heard.
The jury was told about a man called Tom Stephens who was arrested and subsequently released without charge by detectives investigating the five deaths before Wright himself was charged.
Barrister Mark Fenhalls, part of Wright's defence team, told the court that Mr Stephens had said to officers that "if it had been me, I would have strangled them".
Mr Fenhalls said Mr Stephens was arrested on 18 December 2006 shortly after he called police and told them he was "worried about whether he had a split personality and if he was 'doing things which he doesn't know about, then going back to his normal personality'".
Steve Wright, 49, denied killing the five women
Earlier Mr Stephens had told officers he had had an arrangement with Tania Nichol whereby he would do small jobs for her in return for sexual favours, the court heard.
The court also heard Mr Stephens told his employers he "had sex with all five girls and acted as a taxi service for all of them".
"From police inquiries it has not been possible to establish an independent alibi for Tom Stephens for any of the nights on which it is alleged the five women disappeared," said Mr Fenhalls.
Mr Stephens was not charged with any offence in relation to the deaths of the five women and he has always denied any involvement.
But if it was not Mr Stephens could it have been someone else?
In the prosecution's closing statement, the Crown reiterated the possibility that an accomplice had been involved.
Prosecutor Peter Wright QC asked: "Was more than one person involved?.
"We say the answer is simple. We may never know. No-one saw the crimes being committed."
The only person who knows the answer is Steve Wright.