A man who was convicted of murdering his girlfriend on the basis of a confession to an undercover police agent has begun his appeal against conviction.

Wim S. was jailed for 18 years by judges in Breda two years ago for killing 34-year-old Heidy Goedhart at their home in Kaatsheuvel, Noord-Brabant, in 2010.

The breakthrough in the case came when S. admitted to the killing while on a trip to Spain with a man he knew as Joep. In reality Joep was a police officer who had spent a year befriending S. as part of the investigation.

Joep won his target’s trust by posing as a security firm manager who was hiring staff. Knowing that S. was in financial trouble, he let him carry out some small jobs before suggesting he applied to the head of the company, which was based in Marbella.

During the interview in Spain, the ‘boss’ said he knew about the murder but was prepared to overlook it. S. denied being the killer, but later, in the taxi to the airport, he confessed the crime to Joep.

Some legal experts have cast doubt on the reliability of the confession, which S. later withdrew. Legal psychologist Harald Merckelbach told NRC: ‘Leading on a suspect, as happened with Wim S., is another way of exerting pressure.’

S. protested at his trial in May 2016: ‘I am innocent, you’ve got the wrong man’ and vowed to appeal. The public prosecution service has insisted his confession is genuine and has asked the appeal court to uphold his 18-year jail sentence.