A police force is to appeal against a human rights ruling that it failed to protect a witness murdered just days before he was due to give evidence.
Giles Van Colle was shot three times
In March the parents of Giles Van Colle, 25, won £50,000 in damages from Hertfordshire Constabulary over the death of their son.
The optician was shot dead in 2000, a few days before his former employee Daniel Brougham stood trial for theft,
The police apologised but denied Mr Van Colle's human rights had been breached.
Brougham was jailed for life for Mr Van Colle's murder in March 2002 and his appeal was dismissed in May 2003.
He had been employed by Mr Van Colle - who was shot three times at close range - as a laboratory technician at his shop in Mill Hill, north London, for three months during 1999 but was dismissed after equipment was stolen.
Hertfordshire Constabulary accepted disciplinary tribunal findings that the officer in charge of the case - Det Con David Ridley - had "failed to perform his duties conscientiously and diligently".
But the force denied liability and refused to accept there had been a breach of the human rights of Mr Van Colle or his family.
In the landmark ruling in March the judge found the police had acted unlawfully, in violation of Article 2 and Article 8 of the Human Rights Act, by failing to discharge their positive obligation to protect Mr Van Colle's life.
She said if Mr Van Colle had been placed in temporary safe accommodation pending the trial it was "very unlikely" that the murder would have taken place.
Ahead of Monday's hearing at the Court of Appeal in London, Mr Van Colle's father Irwin said: "If the judgment we won is upheld it will have a significant impact, beyond the impact it has already had on the police.
"It will become a textbook case in human rights, affecting not only the police but any other public sector organisation in which there is a duty of care implied beyond that which everybody thinks there is."