Published Thursday, 02 February 2012
The 48-year-old PSNI officer was shot dead in Craigavon in March 2009.
He was nearing the end of his 12-hour shift when he was sent to a 999 call-out at Lismore Manor, Craigavon where a gunman was lying in wait 50 metres away.
Witness M appeared via video link at Belfast Crown Court on Thursday.
While giving evidence the previous day, he told the court that he saw one of the defendants, former Sinn Féin Councillor Brendan McConville, at the scene of the killing before Constable Carroll was gunned down.
Witness M said he was walking in Craigavon with his family and dog when he saw Mr McConville at an electricity box. When cross-examined, the Witness denied having alcohol and eyesight problems.
McConville, 40, from Glenholme Avenue in Craigavon stands accused of the murder alongside 20-year-old John Paul Wootton of Collindale in Lurgan. The pair deny the charges against them.
On Thursday, the witness said that he only wears glasses as a fashion accessory.
However, a defence QC questioned him about this.
"You were told by an optician that you were very short sighted, why did you lie on oath?"
The witness denied telling lies.
The lawyer continued: "How many lies do you have to tell as you go along? You say the person I am representing was close to scene of the murder."
Witness M said, "Something like that you don't forget."
The issue of money was also raised in court with the defence QC asking Witness M how much money he was earning before entering the Witness Protection Scheme.
"£230 before tax," he replied.
When asked how much he received on the scheme, the Witness replied, "£210 a week."
It was also revealed that since joining, witness M has been moved to a new house, his rent and child car costs are paid for him and he has also received two loans from the police for a new kitchen and car.
Witness M claimed the car loan had been paid back and that he was paying £50 per week towards the kitchen loan - although he did not know how much was still outstanding or if there was any interest on the loans.
He denied having debts of nearly £11,000 before he became a protected witness.
Meanwhile, Wootton's mother Sharon Wootton, also from Collindale, Lurgan, faces a charge of perverting the course of justice on dates between 8 March 2009 and 20 October 2009.
It is alleged that she gave false information to police and "removed a computer or computers from her home address believing her home address might be searched and the said computer or computers seized by police".