Paul Grayson, 51, was today told he faces a prison sentence of "considerable substance" after he admitted offences against four patients who had undergone surgery at the hospital, one of whom has never been identified from the footage.
Sheffield Crown Court heard how Grayson - a charge nurse with more than 25 years' experience - also pleaded guilty to filming four nurses and a support worker using a toilet at the hospital, with other unidentified women featuring in this footage who have also not been identified.
He also filmed two other young women with hidden cameras who were not connected to the hospital.
One of them faced Grayson directly in court on Monday and told him his "sick and disgusting perversions" and "evil actions" over four years were crimes that "have torn me into pieces".
Prosecutor Michael Smith told the court how it was this woman's suspicions that led her to conduct her own investigation which uncovered a stash of computer files, "curated" into folders.
Some of the videos that were uncovered had been manipulated to include slow-motion segments, Mr Smith said.
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The prosecutor said that one victim was unconscious after an eye operation when Grayson filmed her up her gown and could be seen moving her underwear, which led to him being charged with sexual assault as well as voyeurism in her case.
Mr Smith said the woman told police she had "put her trust in staff at the hospital to keep her safe".
He said the woman said that she has since been due to have an operation at another hospital, but she "can't bring myself to go".
The prosecutor said one nurse who was filmed in the toilet at the hospital said she had been left "mortified, embarrassed and humiliated".
Grayson, of Woodstock Road, Sheffield, pleaded guilty to 14 charges of voyeurism, three sexual assaults, one charge of upskirting, one of taking indecent images of a child, one of installing recording equipment for the purposes of sexual gratification and three of possessing indecent images of children.
The court heard how the hospital-based offences took place between 2017 and 2020, but there was evidence the defendant had been filming women as long ago as 2012.
Judge Jeremy Richardson QC said he will pass sentence on Grayson on Tuesday, and told him to expect to be in prison for a number of years.
Judge Richardson said the fact he preyed on vulnerable patients who were unconscious in hospital was "the really serious aspect of this matter".
He said: "That's why they feel so utterly betrayed and damaged.
"It's a grotesque breach of trust."
The judge told Grayson: "The real issue in this case is the total sentence to be imposed upon you.
"I do not intend to rush to judgment as there are a number of factors I must weight with care.
"Please but under no misapprehension, the sentence in this case, on any analysis, will be one of considerable substance. It has to be."
Grayson was remanded in custody.