Police are carrying out enquiries at nearly 100 locations in Groningen as they step up efforts to solve a murder case from 24 years ago.

Els Slurink, a 33-year-old psychologist, was found dead in her home on Van Brakelplein on March 21, 1997. She had been stabbed in the heart. Neighbours raised the alarm after she failed to turn up for an appointment at work.

Police told the Asser Courant last week that they had received 14 new tips in response to a new appeal, but none had given them a breakthrough.

‘We follow up all tips and have spoken with a number of those who contacted us. Some of them referred to certain people who may be of interest to us,’ said Rein Ramaker, head of the cold case division.

A DNA sample taken from under Els’s fingernails with traces of an unknown man has also been sent to the Dutch Forensic Institute (NFI) to be analysed using more modern techniques.

The case is the first to feature on this year’s cold case calendar, which police publish every year in an attempt to crack historic cases. Copies are displayed in various locations, including prisons, with details of how to contact the investigation team.

Officers hope that the new inquiries will prompt people with knowledge of the case to break their silence after two decades. ‘Previous research into cold cases shows that the offenders in these cases often tell people close to them what they did,’ a police spokesman said.

We think there must be people who know more about Els’s death and may even be able to tell us who is responsible.’