FOR two decades Elizabeth Roberts has devoted her life to seeking justice for her sister Marjorie Roberts, who was found dead in the River Clyde, in the centre of Glasgow.

Her death, like those of seven other sex workers in the city between 1991 and 2005, remains unsolved. The killings terrified the city as fears of a serial killer stalking Glasgow's redlight area took hold.

Roberts has refused to let the files on her sister's death gather dust among the other unsolved cases.

Her persistence has paid off and the 51-year-old from Cardonald, on the south side of the city, has identified who she believes is a "forgotten suspect" and named him to the Sunday Herald. The man Roberts's family have identified was the last person seen with Marjorie on the night of her death. He was a violent and regular user of prostitutes and a week later was accused of trying to push another sex worker into the Clyde.

She said: "I won't let him get away with it. My sister was murdered and the man who killed her is out there, laughing at us, thinking he has got away with it.

"We know who he is. He is a beast and a monster. He robbed three young children of their mum and took away my sister. I won't allow my sister to be forgotten. She was murdered."

Eight prostitutes, including Roberts, all died in suspicious circumstances in Glasgow between 1991 and 2005, but there has been only one conviction.

Despite a lengthy investigation, police failed to determine whether Roberts had fallen into the River Clyde or was pushed, and eventually detectives concluded "no criminality has been established".

The recent developments in one of the other infamous redlight murders - the killing of Emma Caldwell - have given the Roberts family renewed hope they might see justice one day.

Roberts said: "I have read that girl's murder is being properly looked at again. I want that to happen for us. My sister was murdered and we know who did it.

"I finally feel we may get the justice we've been waiting for after all these years."

It is 20 years since Majorie Roberts, a 34-year-old mother-of-three, died and her sister - despite clinging to hope - has had little to be hopeful about.

First of all she had to convince police that her sister would never have willingly gone into the river and force them to accept that the death was, indeed, suspicious.

Since then she has had to deal with the anger and frustration of not knowing how and why her sister died, and the feeling of being deprived of justice, on top of the unbearable grief.

Roberts said: "Maj would never have gone into that water willingly. She hated water, she wouldn't even put her head near the water if she was in the bath.

"So there's no way Maj would have gone into the river, there's no way she would have left her children behind.

"The detective asked me 'was it possible she willingly went into the water?' and he said he could tell from my face, before I even spoke, that the answer was no.

"Maj would never have left her family, especially her children.

"After Maj died, I spent weeks up the town, speaking to the girls and trying to find out what had happened.

"I knew she had been killed, taken from us by a monster."

In the months before her death, Roberts was bringing up her three children alone. She had split from their father and, after being made redundant from her machinist job, she turned to "street working" for some extra money.

After her death it emerged that she was a drug user and had allowed prostitutes to use her home to take drugs.

"It was hard," her sister said. "To see my sister labelled a prostitute and a hooker, was very hard.

"She was a mother, a daughter, a sister, not a prostitute.

"Maj had only recently started going up the town with the other girls. She had barely been with anyone, but everyone presumed otherwise."

To raise some extra cash to pay her bills, her rent and take care of her three children, Roberts was forced to find work on the streets.

It was at the height of the notorious sex worker killings, but Roberts felt she had no choice.

In August 1995, the 34-year-old went out to work in Glasgow city centre.

CCTV footage showed her with a man on the Broomielaw. That was the last time she was seen alive.

The next day, her body was found floating in the River Clyde, near Jamaica Bridge.

A postmortem examination found no marks or bruises on Roberts' body.

A police insider said: "There was nothing to say she didn't slip and fall into the water and drown.

"It couldn't be proved either way.

"There was nothing to say she was killed, but on the other hand, there was nothing to say she wasn't killed.

"Officers had to leave no stone unturned given what was happening to working girls in the city at the time."

The man Roberts was last seen with quickly became the focus of the investigation.

Despite being interviewed by police, he was released and no charges were ever brought in the case.

Weeks later, the same man was accused of trying to push a prostitute into the river.

The victim managed to get away and flagged down a taxi driver, but she didn't want to take any action over the incident.

Roberts said: "There are so many unanswered questions. The man Maj was last seen with in Calton Place [near the court house on the banks of the Clyde] was questioned but he denied knowing my sister ... That was a lie.

"Her handbag was never found. Police divers went into the River Clyde and couldn't find her bag and it never washed up anywhere either.

"We believe her handbag was stolen by her killer. And for him to be accused of a similar incident not long after my sister died, I mean, what are the chances?"

Last night, Police Scotland insisted the case remained open.

Roberts' sister, however, said officers should now explain why he was ruled out of their inquiry.

She said: "I can't understand why a man who lied and changed his story, said he didn't know Maj, then admitted knowing Maj, wasn't questioned more, or pressed on what he knew."

Roberts claims there are several holes in the suspect's story, including the length of time he spent with her sister the last time she was seen alive.

She said: "He said he walked along the Broomielaw with Maj and it only took a matter of minutes.

"And after speaking to him, the police went out and retraced his steps.

"They told me it didn't add up. His version of events and the time the walk took didn't match up with what the police found out."

The insider added: "The first two people police look at when investigating a suspicious death or murder are the victim's partner and the person they were last seen with.

"It would seem the man Marjorie Roberts was last seen with is highly suspicious."

Other prostitutes, who worked with Roberts at the time of her death, said the man was well known to the sex workers in Glasgow city centre as "a customer".

One said: "He was known for being rough and being violent. That seemed to be his thing. I don't know, but maybe the roughness was part of the thrill for him. He had no respect for women and he made that perfectly clear."

The woman also described how the man would trawl Glasgow's red light zone, which was known as "the drag".

She said he was a habitual prostitute user during the 1990s.

Roberts' family have lived the last two decades with the burden of believing they would never see justice, however, the revelations about the potential suspect have given them hope.

The family say they have spent the past 20 years in the dark, feeling abandoned, but now they see a ray of light after securing information about the potential suspect and meeting with detectives.

"All we want from them is to have to look at him again," pleads Roberts. "My mother needs some peace of mind. We all do.

"Our family was torn apart when Maj died. Since then, everything has been turned upside down and we're living in limbo.

"It's been 20 years and we're still in the same place 20 years on.

"We know he was with her, we know he was with the second woman, who managed to get away.

"We know he was spoken to by the police and we know he lied.

"We want justice. We want answers. We deserve it - for Maj."

The Roberts family met with Police Scotland officers last week and have been assured the inquiry into the mother's death will never be closed.

A Police Scotland spokeswoman said: "It is vitally important to us that Marjorie's family find out how she died and we continue to liaise with them.

"Police Scotland remains committed to establishing the full circumstances around her unexplained death."