McCullagh was questioned about a gaming stream on YouTube he initially said was live.
The PSNI officer said: “From four o’clock on the 18th of December, you were telling the world you were going to be live streaming from 6pm to midnight”.
The officer said: “Your device has been examined and there is nothing to suggest you were on that device between six and midnight.”
McCullagh replied: “That is literally impossible, because you can see it on YouTube.”
A police officer told McCullagh: “You were saying you were live, that’s not the case mate.”
The court heard that later in a pre-prepared statement from his solicitor, McCullagh admitted the stream was pre-recorded.
He said he “recorded the stream and put it out on the 18th”.
“I drank a large bottle of Buckfast,” he added.
“My computer streamed the recording and I slept.
“I woke up to put the bins out.”
In the statement, McCullagh said “the suspect took a taxi to my house, it is obvious the killer of Natalie tried to link me to Natalie’s murder”.
He said he was “shocked” to learn that Natalie was texting other men.
He said: “We were expecting our first child.
“I carried a picture of the scan and Natalie in my wallet”.
During cross-examination of Det Ch Insp McGuinness, the officer leading the murder investigation, was asked by John Kearney KC: “There was no telephone messages in which Natalie was complaining about the defendant?”
He replied: “I don’t recall any.”
Kearney replied: “Nothing in comparison between Natalie and her ex-boyfriend.”
McGuinness also acknowledged that he would have been interested in assessing material from Natalie’s ex-boyfriend’s phone, however it had been wiped by him shortly after her death.