Mr Jenkins, 40, who denies murdering Billie-Jo Jenkins, told Lewes Crown Court he did not know what had happened when he found his foster daughter's body at the family home in Hastings, East Sussex.
Camden Pratt, QC, for the prosecution, said: "Your daughter, you say, was murdered by a man who came over the back or through the front."
Mr Jenkins said: "I didn't say that."
Mr Pratt: "Isn't that what you believe?"
Mr Jenkins: "I don't know how my daughter was killed. I don't know what I believe. I do not know who murdered my daughter. I don't know how somebody got access to my house. I don't know how somebody went at my daughter. I do not know how that was done."
Mr Pratt insisted: "But you must have a theory."
Mr Jenkins said: "I don't have a theory. Of course, it interests me how she was killed. I have not got a theory. I have speculated as to how somebody might have got there, but I don't know. I have never been in a situation like this. I am not a detective. I wanted to help the police."
The prosecution alleges that Mr Jenkins bludgeoned Billie-Jo to death with a tent-peg as she was painting the patio doors of the family home on 15 February last year.
He then went on a "pointless" shopping trip with his two older natural daughters, Annie and Lottie, in order to distance himself from the scene, it is alleged.
Mr Jenkins told police he had gone to a local DIY store to buy white spirit but after a circuitous route realised he had no money and returned empty-handed. Detectives have told how they found a two-litre container of white spirit already in the house. Asked if he had seen pictures taken by police of the white spirit in a cupboard, Mr Jenkins said no.
Mr Jenkins was also questioned about an incident while Billie-Jo was painting when he showed her how to be tidier with the paint. The girl climbed on to his shoulders as he was squatted down by the patio doors.
Mr Pratt asked: "How did you react to that?"
Mr Jenkins replied: "With not much of a reaction really. I might have said it wasn't the place or time to be doing it but I wasn't surprised."
Mr Pratt said: "What did you think she was doing? This 13-year-old girl putting her legs over your shoulder?"
Mr Jenkins: "Billie-Jo was in a very ebullient, excited, happy mood. It was jovial. She was just having fun."
Mr Pratt said: "Do you think that in putting her legs over your shoulder she was trying to flirt or tease with you?"
Mr Jenkins: "She was not. Not at all."
Jenkins was later asked to read from notes he had made in the days after the murder in order to help himself make a witness statement to police.
Despite earlier telling the court he could not remember how he had got paint on his fleece jacket, in the notes he says he can remember Billie- Jo laughing when he got paint on his jacket as he helped her.
Mr Pratt said: "May I bluntly suggest to you that there was no laughing or humorous incident when Billie-Jo caused you to get paint on your jacket."
Mr Jenkins replied: "I understand what you are saying. I cannot be sure how the paint got on my jacket."
Mr Pratt replied: "May I suggest that you got paint on your cuff when you attacked her, not as you suggest."
Mr Jenkins: "And you would be wrong."
The case continues today.Reuse content