The murder-trial witness didn't know that his "aunt" in the Montreal household was in fact his father's first wife, although she had lived with the family for more than 20 years.
His older, sometimes suicidal sister, who died in a mysterious drowning incident along with three other relatives, was in reality extremely happy; her complaints to teachers and social workers were fabricated, he insisted.
And as for the lies the increasingly rattled witness told to teachers, social workers and, later, to Kingston detectives as they delved into one of the strangest homicide investigations ever encountered by Canadian police – well, there was a reason for that too, he explained, his arms folded defiantly as he stared at his adversary.
But the lead prosecutor didn't buy any of it during his withering cross-examination of the crucial defence witness, who by day's end seemed to have damaged his case far more than he had helped it.
And the message from Crown Attorney Gerard Laarhuis to the attentive jury was crystal clear: You are being asked to believe a pack of lies.
Nor did it end there. The witness – one of the sons of an Afghan-Canadian businessman accused of murdering four members of his family in a so-called "honour killing" – will be back in the witness box again Wednesday.
The evidence came from a teenager, his identity shielded by court order, who is one of the seven children of Mohammad Shafia, 59, and Mr. Shafia's second wife, Tooba Mohammad Yahya, 42, who together with their eldest son, Hamed, 20, are each charged with four counts of first-degree murder.
The trio stand accused of drowning three of the couple's daughters, Zainab, Sahar and Geeti, aged 19, 17 and 13, together with Mr. Shafia's first wife, Rona Amir Mohammad, 52, who lived with the rest of the 10-member family in a clandestine polygamous marriage.
The four victims' bodies were discovered in a Rideau Canal lock, east of Kingston, in a submerged car, as the group returned home from a short vacation in Niagara Falls, travelling in two vehicles.
Tuesday's evidence marked a tense day at the ornate Frontenac County Court House in downtown Kingston. Gone was the young man's confidence when he testified Monday, fielding friendly questions from the three defence lawyers.
Instead, as Mr. Laarhuis aggressively went through a long list of problematic statements made by the witness, the most frequent responses were, "I can't remember," and "I don't know" – phrases repeated dozens of times.
"You want to change your testimony now?" Mr. Laarhuis asked sarcastically at one point.
"No, not at all," was the response.
But in one regard, the witness seemed to have full confidence. "I know for a fact that this was an accident," he said of the four deaths.
Among the most damning components of the prosecution evidence is a Google search on Mohammad Shafia's laptop, just 10 days before the deaths, inquiring about "Where to commit a murder."
He had probably done that himself, the witness testified, speaking in fluent English he learned in Dubai, where the Shafia family lived for many years.
Why would he do that, he was asked? Because he was feeling suicidal, he said, but didn't know the correct word for "suicide."
Yet according to his own testimony, he was feeling very cheerful at that point in his life. Yes, there had been problems in the family, but all of them had by then been resolved, he said.
Rona Mohammad, his father's first wife, was also in good spirits when the family set off for Niagara Falls, the witness testified. Whatever her status, she was an equal within the big household – a statement entirely at odds with her torment-filled personal diary, which is a court exhibit.
But most important to the prosecution case are the events on the day the four women died – June 30, 2009.
A few hours earlier, the family had rented two rooms in a nearby motel, where the defendants later insisted that all 10 members checked in; the prosecution contends they did not, that the victims never made it to the motel but rather were murdered at the Kingston Mills Locks.
And central to the defence position is a statement made to police by Tuesday's witness to the effect that, in the early hours of the morning at the motel, his soon-to-die sister Zainab came by his room to borrow his cellphone. He has testified that he is sure that's what happened.
But in his initial police statement, made a few hours after the bodies were found, he said it might have been his mother who asked for the phone.
Mr. Laarhuis also grilled him about wiretapped conversations he had with his brother Hamed, shortly before the three defendants were arrested.
What, for example, did he mean when – clearly very worried he said to Hamed: "Look Hamed, you are 100 per cent caught"?
No clear answer was offered.
And why did he also stress to his brother that he was not aiding authorities as they probed the suspicious deaths.
"Four of your family members are dead and you call your brother – before he's arrested – to tell him you're not helping the police, why would you do that?" Mr. Laarhuis asked. "What is it you weren't supposed to talk about to the police?"
"I don't know," the witness replied.
Equally striking during those lengthy wiretapped exchanges was that neither of the two brothers – who were close – expressed any curiosity about what might really have happened to their relatives.
"Not once did you hint that someone else might have been responsible for your sisters' deaths," the prosecutor said.
That's because he knew "for a fact" that an accident had taken place, the young man responded.
And perhaps most puzzling was his vague account of how the family had stopped at the lock, on the first leg of the journey, heading to Niagara Falls.
The prosecution theory is that a reconnaissance trip was afoot; cellphone records show the travelling family stopped there for about 40 minutes.
But the witness could barely recall anything about the pit stop, where he said some of the group wanted to use the toilets.
He didn't know how they got there and wasn't sure if he had ever been there before; he couldn't recall who it was who visited the bathroom; he couldn't describe the nearby buildings, even though it was still daylight, because "I wasn't paying attention."
He got out of the car briefly "to stretch my legs," he testified.
Did he see any water nearby?
"Yes, no, I don't know," was the reply. "It was three years ago. … I can't guess stuff."