BRATISLAVA (Reuters) - Slovak police may have inadvertently destroyed evidence through negligence at the scene of the murder of an investigative journalist, his family’s lawyer said, in a case that prompted mass street protests and the prime minister’s resignation.

Journalist Jan Kuciak, who had written about political corruption in Slovakia, was found shot dead along with his girlfriend at their home in February. They were both 27.

As well as forcing the resignations of veteran prime minister Robert Fico, his interior minister and Slovakia’s police chief, the case also exacerbated worries about media freedom in ex-communist eastern Europe.

No one has been charged with the murder, which a prosecutor has said was probably a contract killing.

The Kuciak family’s lawyer, Daniel Lipsic, a former Slovak interior minister, said the two bodies had been moved without being examined by a forensic surgeon at the crime scene and this led to an incorrect initial pronouncement of the time of death.

“I don’t understand why more experienced investigators from the National Crime Agency (NAKA) were not called immediately, and arrived at the crime scene hours after the district police,” Lipsic told Reuters in a telephone interview late on Thursday.

“Some evidence was not secured immediately but was only discovered in photographs from the crime scene,” said Lipsic, who served as interior minister in 2010-2012.

“This is a serious dereliction of duty. We don’t know how much evidence may have been destroyed,” he added.

Pictures from the crime scene published by the Slovak media also show that NAKA’s anti-corruption section chief, Robert Krajmer, who does not directly investigate murders, was also present.

The police first denied Krajmer was at the crime scene and later issued a corrected statement saying he had “carried out tasks related to the investigation”.

Asked about Lipsic’s criticism, the police said only prosecutors could comment on the case.

The special prosecutor’s office said “some failures were detected during initial actions at the crime scene”.

Kuciak had, among other things, investigated fraud cases involving businessmen with Slovak political ties. He had also looked into suspected mafia links of Italians with businesses in Slovakia.