A Dorset Police officer whose affair with a domestic violence victim was blamed for her murder has been thrown out of the force.

PC Richard Allan was assigned to protect Kat Ryba from her partner Piotr Zasada.

But when Zasada found out they were having an affair, he flew into a jealous rage and stabbed her several times in front of their three-year-old daughter before hurling her out of a second floor window, his court case heard.

An investigation by the Independent Police Complaints Commission (IPCC) identified failings by PC Allan and other police officers and revealed the force’s domestic abuse policy was also out of date.

But it concluded the failings “did not directly impact on the eventual tragic outcome”.

The inquiry revealed PC Allan deleted text messages he had exchanged with Ms Ryba once he discovered she had been murdered and carried out unauthorised searches on the police computer after being removed from frontline duties while the matter was investigated.

He was dismissed from service after facing a police misconduct panel in June but the information has only just been released by the IPCC.

Ms Ryba, 26, was staying with her daughter at a friend’s flat in Wellington Road, Bournemouth when the horrific attack took place in October 2009. Zasada pleaded guilty at Winchester Crown Court last year and was sentenced to life imprisonment.

Prosecutor Anthony Donne QC told the court: “He was angry at her for leaving him and was jealous that she had started an association with another man.

“The police are there to provide vulnerable people with comfort and support. The line is extremely obvious and PC Allan overstepped that line.”

The IPCC inquiry also discovered the domestic violence risk level in the case was identified as medium but was incorrectly recorded as standard. A non-molestation order was not recorded on the Dorset Police or national police computer systems and the domestic violence policy and procedure were out of date.

A Dorset Police spokesman said: “The IPCC investigation identified a number of issues with the way that several officers, including police constable Richard Allan, handled domestic abuse complaints made by Ms Ryba.

“It was also concluded that the identified issues did not directly impact on Ms Ryba’s death.

“Dorset Police welcomes the Commission’s findings and has made changes to further improve the way that the force handles such reports – such as updating the relevant policy and providing words of advice to officers and staff.”

Following Ms Ryba’s death, PC Richard Allan was moved to non-operational duties and placed under close supervision.

In June 2011 he was dismissed from the force.

“It is essential that all Dorset Police employees adhere to the high standards of professional behaviour expected when dealing with victims of crime.

“In this case a misconduct panel found that PC Allan’s behaviour was not in keeping with these standards.”