The couple were shot dead in their bungalow
An inquest jury has been asked to consider if police corruption played any part in the deaths of a Lincolnshire couple.
John and Joan Stirland were killed in a revenge attack in August 2004 after Mrs Stirland's son shot a friend of Nottingham crime boss Colin Gunn.
Gunn has since been jailed for 35 years for conspiracy to murder the couple.
Coroner Karon Monaghan asked the jury to investigate whether the police failed to protect the Stirlands.
Jurors, who were sworn in earlier, are being asked to examine whether police dealt with intelligence properly.
They will also hear how the Stirlands' address was disclosed by a BT employee.
Colin Gunn was jailed for 35 years
Mrs Stirland's son, Michael O'Brien, is being allowed to watch the proceedings in jail, where he is serving his life sentence for murder.
The Stirlands fled to Trusthorpe on the Lincolnshire coast from Nottingham, after O'Brien killed Marvyn Bradshaw, 22, outside a pub in Bulwell, Nottinghamshire.
Before the couple fled Nottingham, shots were fired into their home.
Gunn, 40, of Nottingham, was jailed in 2006 following his conviction for conspiracy to murder the Stirlands.
Co-defendants John Russell, 29, and Michael McNee, 22, were jailed for 30 and 25 years respectively, in 2006.
Inquest looks at revenge killings