A couple have been convicted of murdering a homeless woman whom they drowned in their bath before claiming her benefits.

Kevin Flanagan was charged alongside his girlfriend, Kathleen Salmond, with killing Lisa Bennett after his brother told police his sibling had confessed to carrying out the crime.

Salmond, who appeared via video link, was also found guilty of benefit fraud between 8 and 31 May 2013 and preventing Bennett’s burial – charges Flanagan had previously admitted.

The pair collected £4,979 in benefits while maintaining the pretence their 39-year-old victim was still alive.

Lisa Bennett. Photograph: West Midlands police

Flanagan, 39, of Kings Norton, Birmingham, and Salmond, 40, of Hodge Hill, Birmingham, were convicted on Wednesday after a trial at Birmingham crown court. Jurors heard how the victim was told she would be eating her “last dinner” while afterwards her body was “callously” dumped in a wheelie bin.

The remains were then “incinerated” at a community waste facility, the prosecuting barrister, Simon Denison QC, told the jury of nine men and three women. No trace of Bennett’s body has been found.

Salmond, who is now largely confined to a bed or wheelchair, and Flanagan carried out the killing at their flat in Weoley Castle, Birmingham, on or around 9 May 2013. The jury heard how the defendants then “reaped the benefit of Lisa’s disappearance”, after Salmond phoned the Department for Work and Pensions, pretending to be Bennett, arranging for £230 in benefits to be paid into her own account.

Flanagan also used the victim’s phone to text her mother “to make her believe that nothing had happened and Lisa was alive”, prosecutors said. When questioned over the disappearance, the couple “calmly” told police Bennett was “alive and well” and that she had asked them to transfer her benefits into Salmond’s account.

The pair also claimed a fictitious boyfriend of Bennett’s, who they named Ian, was collecting the cash each week. Jurors were told Bennett was a drug addict and alcoholic, who was last seen collecting a prescribed heroin substitute from a pharmacy.

Under cross-examination from Salmond’s barrister, Flanagan insisted he told his brother Bennett “died from an overdose”. But jurors convicted Flanagan and his co-accused after a trial lasting just over three weeks.

As he was found guilty, Flanagan, who had numerous previous convictions going back more than 20 years for theft, robbery and shoplifting, did not react. Salmond, who has a history of offending going back to 2010 with convictions for assault and battery, did not appear to react as the verdicts were returned.

Opening the case against the defendants, Denison said: “Lisa died in their flat, on or around May 9 2013. Her body has never been found. She has no grave. The prosecution case is that the defendants murdered her, and then callously disposed of her body in the communal bins opposite their flat, where it lay undiscovered before the bins were emptied and the contents were taken to the council waste disposal facility a few days later.

“There, her body was incinerated with the community’s waste. What they did, we suggest, was carry out a plan: to kill her, to conceal her body so it wouldn’t be found, to lie and lie and lie in pretending that she was alive, and to take her money for themselves.”

He added: “It is an almost inhuman thing to do, is it not, to treat not just a human body but the body of someone they knew, as a piece of rubbish to be thrown away?”

The couple’s crimes were only uncovered when Flanagan’s brother came forward in 2014 after seeing a televised public appeal for information about Bennett.

Denison said: “When he saw the TV appeal he realised what his brother had told him was true, and seeing Lisa’s mother not knowing what had happened to her daughter – when he did know – had affected him to the extent that he had to come forward, even though he said he loved his brother.”

Flanagan and Salmond will be sentenced on Friday.