The families of five slain Ipswich prostitutes angrily demanded the return of the death penalty today after a former pub landlord was convicted of their murders.

After a six-week trial, a jury at Ipswich Crown Court took just eight hours to find Steve Wright, 49, guilty of the murders of Gemma Adams, 25, Tania Nicol, 19, Anneli Alderton, 24, Paula Clennell, 24, and Annette Nicholls, 29.

The remains of the five women were found in isolated spots near the town during a 10-day period in December 2006. It was the most intensive murder spree in British criminal history and left thousands of other women in fear for their lives.

But although Wright faces at least 30 years in jail – prosecutors called for a "whole life term" – the victims' families said in a joint statement read out by a police liaison officer that he should have faced the death penalty for a crime so serious.

"Today, as this case has come to an end, we would like to say justice has been done but we are afraid that whilst five young lives have been cruelly ended, the person responsible will be kept warm, nourished and protected," they said.

"In no way has justice been done. These crimes deserve the ultimate punishment and that can only mean one thing."

Sentencing is set for Friday.

Detectives launched an inquiry after Nicol vanished in late October 2006. It rapidly grew in scale after the disappearance two weeks later of Adams.

The discovery of their bodies, followed by that of Alderton, who had not even been listed as missing, meant that the Suffolk force had a major murder investigation on its hands.

Prosecutors said Wright "systematically selected and murdered" the prostitutes over a six-and-a-half-week period. They said he stalked the red-light district near his home when partner Pam Wright, 59, was working nights at a call center.

Wright, a former steward on the QE2, had admitted having sex with four of the victims but insisted that he did not kill them. The trial heard that two of the bodies were arranged with their arms outstretched in a crucifix pose.

Wright was arrested after police matched his DNA – kept on a police database after he admitted to theft in 2003 – with samples collected from sites where some of the victims had been found. Forensic analysis revealed his DNA on three of the women and fibers linking him to all five, the court was told.

After his conviction, police will reopen a number of "cold cases" as they question whether he may have killed before. Five other women have been killed or vanished in East Anglia in the past 16 years, although detectives have not linked any of the killings with Wright.

Dressed in the dark suit, white shirt and pale blue tie he has worn throughout the trial, Wright showed no emotion as the verdicts were read, staring forward and avoiding eye contact with the jurors and family members in court.

There were shouts of "Yes" and sobs from relatives of the women sitting in the public gallery as the verdicts were returned.

The trial judge, Justice Gross, said Wright would be sentenced at 10: 30 a.m. local time Friday. He thanked the jurors for their "time and attention" in what he said was an "extremely disturbing case".

Peter Wright, QC, for the prosecution, called on the judge to impose a "whole life term". He argued that the criteria for passing such a sentence were met because there was "a substantial degree of premeditation or planning" behind the killings and also because of their sexual nature.

Gross indicated that his only alternative in sentencing would be to start on the basis of a life sentence with a minimum 30-year term.

Wright’s brother, Keith, said: "I’m surprised the verdict has been so quick. I would have thought there is enough things for them to have some doubt. I don’t know if surprised at the verdict is exactly the right word. I just didn’t think it would be so quick. Whatever the sentence, it’s all over now."

Commenting on the case, the Crown Prosecution Service said that it may never know why Wright turned to murder. "Quite often in a murder case we do not know the motive or understand it if we do. The evidence leads us to who did it and that’s more important," said Robert Sadd, Crown Advocate for CPS Suffolk.

The case also leaves another unanswered question: Had Wright killed before? Relatives said that he had a history of depression, that he had attempted suicide and that "girls upset him."

Keith Ashcroft, a psychiatrist, said the spree murders could have been a symptom of manic depression, and added "it’s more likely than not likely" that Wright had killed in the past.

"He has a significant history of frequenting prostitutes and also a history of suicide attempts," said Dr. Ashcroft, of the Centre for Forensic Neuroscience in Manchester. "You put that together and it looks like a manic depressive illness.

"In terms of his murder spree, perhaps it was because of a manic spate. Perhaps he wanted more than just sex. It could’ve been a sex game that went wrong for the first one and he decided to do it again and again.

"The fact is, he got sloppy in the end. It may be his manic phase had ended and he couldn’t be bothered to prevent (himself) getting caught."