A man's appeared in court charged with the murder of a retired army officer in Hertfordshire more than eight years ago.
Former Lieutenant Colonel Riley Workman was found shot dead on the doorstep of his home in Furneux Pelham near Bishop's Stortford in January 2004.
Former gamekeeper, Christopher Docherty-Puncheon, is accused of killing the 83-year-old.
Opening for the prosecution at St Albans Crown Court, Richard Latham QC told the jury this was a "whodunnit?" crime. There was no dispute Colonel Riley Workman had been murdered - it could not have been an accident - but the question is can you be sure it was this person, he said.
The person he was referring to was Christopher Docherty-Puncheon who used to be known as Christopher Nudds. A local pest controller who had access to firearms.
Lieutenant Colonel Workman was shot dead on his doorstep at his home in the Hertfordshire village of Ferneux Pelham on the night of 7th January 2004.
His body was found the following day by his carer, who assumed he had died of natural causes.
A paramedic and a doctor had failed to spot his injuries and it wasn't until the undertaker arrived that his gunshot wound was discovered.
Forensic tests later revealed the frail pensioner had been killed at close range by something other than a normal shotgun.
The Prosecution say before the murders, Docherty-Puncheon's uncle found a sawn off shot gun hidden in his car, which he claimed was for shooting deer.
The jury were told about Docherty-Puncheon's previous conviction for the murder of Fred Moss, who was killed at the end of 2004.
They were told not to assume it implied guilt in this case, but the information would enable them to make accurate assessments of future evidence.
The court heard how the home of Docherty-Puncheon was searched during the investigations into both murders eight years ago and while ammunition was found, a firearm was not.
The jury also heard about a mystery 999 call from made from a phonebox in a nearby village hours before the Colonel's body was discovered and how a lorry driver spotted a car similar to the defendant's around the time of the call.
Docherty- Puncheon who is now 33 denies murder.
The case is expected to last 5 weeks.