This video shows a trusted carer stealing from an 86-year-old woman after a secret camera was set up by her suspecting relatives.
Sisters Jodie Faith-Brown and Marie Cole hid the camera in their grandmother's bedroom to unmask callous Susan Stuart as a thief.
Stuart, 60, was repeatedly filmed going into widow Debbie Faith's purse when her back was turned.
She denied stealing £30 between December 2017 and February last year but was convicted by a jury after a trial at Plymouth Crown Court.
After the verdict she was branded "scum" by her victim's granddaughters who helped bring her to justice by setting up the secret recording.
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Plymouth Crown Court heard how Stuart pilfered cash from the victim's handbag while her back was turned.
But she was spotted repeatedly going into her purse on footage from a camera hidden in Mrs Faith's bedroom by her family.
Trusted Stuart, who had been caring for the widow in her home for years, was also caught with a £5 note marked by police.
She claimed that Mrs Faith had given her permission to go into her purse so she could run errands such as posting packages.
A judge released Stuart on bail until sentencing on a date to be fixed with a probation report.
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Judge Paul Darlow said: "This is the theft of small sums of money but it is in gross breach of trust."
Stuart was one of four carers from the company Caremark which visited Mrs Faith every day.
She was suspended and has since resigned.
Footage shown to the week-long trial from a camera hidden on a dressing table showed Stuart repeatedly going into the purse, though she did not take cash on every occasion.
She twice allows Mrs Faith to leave the room in her home in Plymouth, Devon, unaided using her walker - risking a fall.
The family realised that money was going missing on Fridays, the usual day Stuart visited and amassed hours of film.
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Jodie, who is not working, would check the amount of money in the purse before and after the carer visited. She would then wait outside in her car during Stuart's visit.
Speaking after the case, Jodie said "I think she is scum. I think she is disgusting."
The sisters said that it only became clear that money was going missing when they took closer control of her finances in March 2017.
Mrs Faith has been living alone since the death of her second husband Douglas about five years ago.
The court head the sisters hid the camera in a dressing table pointing at their nan's handbag and a money tin.
They also kept a careful count of the cash so they could be certain when money was missing.
And in reference to the famous television detective, Jodie said: "I felt a bit like Columbo."
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Marie, 37, who works with children with special needs, added: "She had been caring for nan for six or seven years. She would have been one of the last ones we would have suspected."
Former shorthand typist Mrs Faith, who moved from London with her husband about a decade ago, has four children, 11 grandchildren and more than 20 great-grandchildren.
Caremark continues to provide help for Mrs Faith in her home.
Marie said they became suspicious as her nan was withdrawing £300 a month - far more than she actually needed.
"This has been a very unsettling and distressing time for my nan and both me and Jodie, but we are so relieved that the right verdict was given.
"My nan's carers do a amazing job giving her the independence to be able to live at home, it was awful having to suspect every carer for a couple of months until we were certain who was taking money.
"We went to the police who advised us to put in a camera, record monies being taken and to get a cash box, which we did.
"We have many recordings of Susan Stuart stealing off my nan always when she was out of the room, behind her back or taking her handbag out of the bedroom where my Nan was asleep.
"I just hope she will not be allowed to work in care again where she can do this to other vulnerable people. We had to suspect every single carer.Nan was being visited by four people every day. There were probably a couple of main carers but probably around six."
The sisters said one of the worst things about Stuart's crime is that she cast suspicion on her innocent colleagues at Caremark.
Stuart herself was suspended and resigned. She is no longer working in care and is likely to be banned from the industry.
She will be sentenced at a later date.
