Anthony Fort, who had become suspicious about his wife Ruth's spending habits, found the bank card in her handbag after being disturbed by her talking in her sleep.
The supportive husband accompanied her to Preston's Sessions House Court, where Recorder Sarah Johnston imposed a 16 month jail term suspended for 18 months, and praised him for his actions.
Fort, who worked at Crystal Hall Residential home in Whittingham, Preston, helped herself to cash withdrawals using the woman's card between October and December 2018.
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Prosecuting, Jack Troup said Fort was employed by the home to assist and care for the victim, who is wheelchair bound and has significant mental health difficulties.
He added: " One of her duties was to take her out on shopping trips and the like, and whilst they were out, because of her difficulties, she would undertake to withdraw money from the cash point for her to spend on whatever she wished.
Mr Fort became concerned she was spending extortionate amounts of money which he didn't think they had during a holiday in Mexico in November 2018.
The court heard on return to the UK the mum-of-one became unwell and was taken to hospital.
Her aunt came to stay to help Mr Fort to care for her, and also expressed concerns about her spending habits after she witnessed the defendant taking out large quantities from a cashpoint.
Mr Troup said: "On December 14 Mr Fort was disturbed by the defendant sitting up in bed and talking in her sleep.
"When he looked across he could see her handbag had been strewn across the floor and a number of £20 notes had fallen out. While returning the contents to her bag he found the cash card."
When he challenged his wife she admitted to taking cash from the woman and explained that was where her spending had come from.
He reported it to the police and the 46-year-old, of Harrowby Road, Birkenhead, has since pleaded guilty to fraud by abuse of her position.
Recorder Johnston said: "The offence you fall to be sentenced for is a serious one.
"You were employed to care for, assist and protect that vulnerable woman.
"You claimed in interview you had committed this offence at a time you were suffering financially in your family unit but I treat that assertion with some scepticism because this offence came to light as a result of your excessive spending whilst on a family holiday to Mexico."
Referring to her husband's actions, she added: "That must have been a very difficult thing for him to do.
"His doing so, and the consequences involved, led to the breakdown of your relationship, though I read you are working to resume your relationship."
She said she had to balance Fort's mitigation with the "revulsion the public feels for individuals in positions of authority who take advantage of vulnerable members of our community for financial gain" and added: "Temptation here very quickly turned into greed."
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