A senior police investigator with 17 years of experience preyed on two women suspected of being sex workers while they were in custody.

In what a district judge called a serious abuse of trust, Lee Sze Chiat, 39, a Senior Staff Sergeant, molested one woman and got the other to perform sex acts on him.

All this happened while the women, both Chinese nationals aged 28 and 29 respectively, were in handcuffs in an interview room at Jurong Police Divisional Headquarters.

Sentencing Lee to a year behind bars and a stroke of the cane yesterday, District Judge Christopher Tan said the fact the molest victim was under restraints cannot be ignored.

"What's aggravating is that these restraints were actually physical strictures that the law empowers policemen to use to protect the innocent," said the judge, who also took into account Lee's guilty plea.

"But they were used to subjugate her to fulfil his desires."

Lee pleaded guilty to one count of molestation and an offence under the Police Force Act.

Two other related charges were taken into consideration.

Deputy Public Prosecutors Marshall Lim and Niranjan Ranjakunalan had sought at least 13 months' jail with caning.

They said the facts of the case were disquieting and it was shocking that an officer of Lee's seniority could commit such abhorrent offences.

The women, who cannot be named due to a gag order, were arrested on Dec 6, 2017, and taken to Jurong Police Divisional Headquarters.

Even though he was not rostered or formally assigned to perform any investigative duties in the case, Lee offered to help when he learnt of the arrests, the court heard.

At about 11pm, he escorted the 28-year-old woman, whose hands were cuffed in front of her, from the basement lockup to an interview room on the first floor of the building.

Directing her to a bench, Lee closed the door and interviewed her, asking her about the "services" she provided.

MASSAGE

When he asked her twice to give him a massage and she refused, Lee locked the door and told the woman there were no CCTV cameras in the room.

He again asked for a massage, and the woman reluctantly agreed, squeezing his shoulders to appease him.

Lee then turned to face her, held her waist and molested her over her T-shirt.

Shocked, she shouted at him to stop and tried to move away.

But Lee persisted, asking her to provide him with "services" while placing her hands over his shorts.

She refused.

After the hour-long interview, Lee met a colleague who was escorting the other woman back to the lockup area after taking her statement.

Volunteering to help complete some investigative tasks his colleague had missed out, Lee took the woman, whose hands were cuffed like the first, to the same interview room and asked her to masturbate him and perform a sex act on him.

Not wanting to turn down a request from a police officer, she ultimately agreed.

Lee's acts came to light after the first victim called the Police Cantonment Complex five days later about extending her Special Pass - issued to foreigners for a specific purpose like assisting in an investigation.

She met a specialised crime branch officer, who advised her to make a police report.

The prosecutors said the case was conceivably one of the most serious disciplinary offences that may be committed by a cop.

Lee had exploited vulnerable victims under his charge and his acts were a callous dereliction of duty, they added.

In mitigation, Lee's lawyer said his client is a transformed man and has been going for counselling with his wife at church, which he regularly attends.

Replying to The New Paper's queries, the police said they have commenced disciplinary proceedings against Lee following his conviction yesterday.

He had been interdicted from service since Dec 26, 2017.

A spokesman said: "(The Singapore Police Force) takes the safety of arrested persons in police custody very seriously...

"This was an isolated case and does not represent the professional and disciplined conduct of the rest of our SPF officers."