MR Brendan O'Donnell told the Central Criminal Court yesterday that he had shot Imelda Riney after the devil told him to because she was "the devil's daughter".
He also claimed to have had a sexual relationship with her.
Mr O'Donnell laughed in court as he told of the scene after he shot Father Joseph Walsh.
He told the court later yesterday afternoon that he was hearing the devil's voice in the courtroom box. The voice was saying Brendan, you're a murderer Brendan, you're the devil's son Brendan, count to one hundred and you'll go deaf.
Mr O'Donnell (21), a native of Co Clare but of no fixed abode, was continuing his evidence on the 32nd day of his trial on 12 charges relating to events in the west of Ireland in 1994.
He has pleaded not guilty to the murder of Imelda Riney (29) and her son, Liam (3), between April 28th and May 8th, 1994. He has also pleaded not guilty to the murder of Father Joseph Walsh (37), the former curate of Eyrecourt, Co Galway, between May 3rd and 8th, 1994, and the false imprisonment of Father Walsh.
Resuming his evidence yesterday morning, Mr O'Donnell said he developed a relationship with Imelda Riney in April 1994. He said she brought food to him over many days while he lived in a tent in the woods.
On other days he would go and visit her in her home. He said he would call to her between 11 a.m. and 3 p.m. before her other son, Oisin, came home from school. He said Imelda would be there with her youngest son, Liam.
"We started getting close to each other", he said. "Liam took to me. He would call me Ben. I would play with him." He was a lovely child, he added.
"I got on great with Imelda", he said. A sexual relationship had started after they sat together on the couch one day and he had kissed her. He said they had sex on occasions in the bedroom of her house and sometimes in his tent in the woods.
Mr O'Donnell said that, during the month of April, he had stolen number of cars and he described burning a car he had stolen in Ennis in Ballynakill Wood "I liked fire and cars burning", he said. "I liked the noise of tyres bursting."
He started to laugh and told the court "I just like fire. It's the devil's work."
He said he was also given a Nissan Bluebird car by a man in Limerick whom he knew from prison. He later left this car in Limerick and bought £40 worth of hash there. He went back to Imelda Riney's house after buying the hash. He said they smoked half of it and afterwards had sex.
He got very close to Imelda. "I, was in love with her", he said. She was in love with him also, he laid.
Mr O'Donnell said he knew from Imelda then that Vale Ballance, her estranged husband, was in Co Clare. That changed things. He could not go to the douse when Mr Ballance's car was here. He said he was still having sex with Imelda after Mr Ballance arrived and had had sex with her four or five times after Mr Ballance came back.
He said he burned the tent he had been sleeping in because he did not want to live in it any more. He would sleep in cars and his grandmother looked after his clothes. He had also slept in a horse box on a farm. He said he got money from his granny and from Imelda.
He said he had gone to see Mr Frank Muggivan in a caravan and while he was there gardai arrived. He got a pick axe handle and told them to back off or he would "blow their heads off" They did back off and he escaped.
Early on the morning of Friday, April 29th, he stole a gun from the house of Mr Edward Jamieson. He said he had decided be would get money. He looked in Mr Jamieson's house for money but could not find any. He found the gun on a press and also a tin of bullets.
He said he had intended to rob the post office at Whitegate to get cash for France. Imelda was going to get him a passport to go to France and he was going to live over there, he said.
He said he walked over the fields to Imelda's house carrying the gun and bullets. He fired the gun at trees on the way and got there about 10.40 to 10.45 a.m.
Imelda's car was at the house but Mr Ballance's was not, he said. He went into the house carrying the gun. Imelda was putting blue wellington boots on Liam. He said Imelda asked him where he got the gun and he said from Mr Jamieson. She told him to put it away because she did not want it around Liam, he said.
He put the gun outside and went back into the house, he said. Imelda put the kettle on to make tea and they had sex upstairs.
While they were upstairs, Liam came up and made a remark he said. "I heard a voice from the devil telling me to kill Imelda that she was the devil's daughter", he added.
He said that Imelda had just gone downstairs and he went "after her and told her he had to kill her because she was the devil's daughter. She had said "Don't be raving, Brendan."
The gun was loaded and he pointed it at Imelda and told her to come with him, he said. Liam was there, too, and was frightened. Imelda was holding him.
He said he told Imelda to drive her car and he got into the back with the gun and Liam. He told her to drive to Cregg Wood.
They drove into the wood and got out of the car, he said. Imelda was very nervous" and Liam was afraid.
"Me, I was happy", he said. "I said Imelda, lie down on the ground, I'm going to shoot you'd".
"She tried to pull the gun off me he told the court. Imelda grabbed the barrel with her fists, he said.
"She pulled the gun, I pulled the trigger and I shot her in the eye and blood started squirting into the air.
"I wanted to kill her because she was the devil's daughter, because the devil told me to do it. I felt very happy, a lovely feeling."
Mr O'Donnell said he had not decided what he was going to do with Liam. "I was in the woods with him on my own", he said. "He was sitting on the ground."
Liam was about 20 yards away when the shot went off. The child could not see his mother and Mr O'Donnell "because of the trees".
Liam had asked "Where's Mammy?"
Mr O'Donnell said he did not want to leave Liam without his mother, as he himself had been left. He brought Liam over to there his mother lay on the ground. "I wanted them to be together", he said. He said he could not look at the child because of his "innocent face" and had shot him in the side of the head.
"I felt happy he wasn't growing up without his mother", he said.