The Corruption and Crime Commission handed down two opinions of serious misconduct on Thursday against Judith Innes-Rowe, who worked for 23 years at Sir Charles Gairdner Hospital as a clinical trials manager.

Staff at the unit she worked in are paid from a special purpose account funded by sponsors including pharmaceutical and biotechnology companies for cancer clinical trials.

"So this money, in the end, was not spent on direct trials," CCC commissioner John McKechnie told 6PR.

She wasn't entitled to claim overtime, but would do so even when she turned up late.

She even claimed double-time-and-a-half on seven public holidays when there was no evidence of her attending the hospital at all.

Ms Innes-Rowe reported to and was trusted by oncology professor Michael Millward, who considered her to be so senior she could determine for herself when to work and didn't have to complete a timesheet.

"The work was getting done and he was not in a position to know of her daily movements," the CCC said.

"He was, however, placed in a position to approve her overtime claims.

"Misplaced trust and familiarity can be the enemy of effective oversight, without which most controls can be circumvented."

The CCC also found that despite not submitting approved leave forms for 125 days of absence, Ms Innes-Rowe was paid out about $65,000 in lieu of annual leave when she retired in December 2018.

Even after two internal reports by North Metropolitan Health Service recommended disciplinary action, she was re-engaged via a recruitment agency the following month.

In addition to a lack of appropriate managerial vigilance, dated technology contributed systemic weaknesses, the CCC said.

Any action to recover the money was a matter for the NMHS, it added. The NMHS is already in the spotlight over a fraud and bribery scandal.

A CCC report last year revealed NMHS bureaucrats John Fullerton, David Mulligan and Shaun Ensor took gratuities -including overseas flights, accommodation and boozy lunches - from 11 contractors for a decade.

The contractors were given ongoing work in exchange.

Five contractors have been charged with various offences and all have pleaded guilty.

But Mr Fullerton - who is at the centre of the scandal and had cash allocated for legitimate Health Department work used to pay for $170,000 worth of renovations at his home - has not been charged.

Mr Fullerton, Mr Mulligan and Mr Ensor pocketed more than $600,000 in redundancy payments when the department knew the CCC probe was underway.

Australian Associated Press