In 2012, a police officer helped a woman friend screen her former boyfriend's travel history as she had suspicions about his diplomat status.

Rishinder Singh Sidhu, 35, was having dinner with his friends, Ms Jessica Ng Kar Lan and Mr Yee Weng Kheong, 60, that year when Ms Ng voiced her suspicions about her former Australian boyfriend Reginald Lee Hum Hang, who allegedly told her he was a diplomat.

Rishinder, then a staff sergeant with Clementi police division, offered to conduct a screening of Mr Lee's travel movements.

He instigated a fellow police officer to search for Mr Lee's travel patterns on the Immigration and Checkpoints Authority's computer system.

Rishinder, a Singapore permanent resident, was yesterday sentenced to five months' jail for abetment of unauthorised access to data, theft and perverting the course of justice.

On Nov 28, 2013, he stole $20 from Staff Sergeant Noor Adnin Sainal, 30, his colleague at Bukit Merah West Neighbourhood Police Centre. Several officers had reported having their money stolen between September and November.

A "mouse-trap'' operation was set up, and Rishinder was caught in the act on a pinhole camera installed at SSG Adnin's workstation, said Deputy Public Prosecutor Ryan David Lim.

In the third case, the court heard that housewife Teo Hwee Leng, 48, disapproved of her 20-year-old son's relationship with his girlfriend, also a 20-year-old student.

While checking his mobile phone on Dec 21, 2014, she found an obscene photo his girlfriend had sent and confiscated the phone. According to Madam Teo, she sent the obscene photo to the girl using her son's phone, and threatened to disseminate it if the girl contacted her son. The girl made a police report .

Madam Teo and her husband, who knew Rishinder, approached him for advice, not knowing he had left the police force in March.

On Dec 26 that year, Rishinder told Madam Teo to delete messages and images of the obscene photograph from her mobile phone, to frustrate investigations into her alleged criminal intimidation.

He also told her to say she did not intend to carry out her threat of posting the obscene photograph online.