The son of a Montreal couple accused of killing their three daughters testified at their murder trial on Monday, laying eyes on his parents for the first time in three years.

As the young man entered the witness box, his parents – Mohammad Shafia and Tooba Yahya – waved and started crying as he waved back.

"His father collapsed in sobs, his body shaking. This went on for several minutes," said CBC reporter Justin Hayward, who is covering the trial at the Kingston, Ont. courthouse.

"His mother, also in the prisoner's box appeared to be so pleased she began to laugh. "

The name of the son cannot be released due to a publication ban.

Tooba Yahya, 42, and her husband Mohammad Shafia, 58, are charged alongside their eldest child, Hamed, 20, with four counts of first-degree murder.

They're accused of killing Shafia sisters, Zainab, 19, Sahar, 17, and Geeti, 13, along with Mohammad Shafia's first wife Rona, 52.

Shafia sibling says brother, father slapped him

Crown prosecutors allege the wealthy Afghan-Canadian couple and their eldest son orchestrated their family member deaths as an honour killing, to restore the family's reputation in light of perceived transgressions committed by the teenaged girls.

The four females were found dead in a car submerged in the Rideau Canal near Kingston in June 2009.

On Monday the jury trial watched a police interrogation video of the young man called to testify. The video was recorded the night Shafia and his wife were arrested.

The son is asked whether there is trouble at home — he admits yes, and acknowledges arguments, describing one occasion where he was slapped repeatedly by his brother Hamed and his father.

When the police officer asks how that would have been dealt with in Afghanistan, the boy responds 'don't ask me, I've never been there.'

Defence could call all accused to testify

Mohammad Shafia testified in his own defence last week and faced tough questions from Crown prosecutor Laurie Lacelle during cross-examination. Shafia told the court he values honour, but that there is no honour in killing.

Expert witnesses testified earlier in the trial that in some cultures, when family honour is threatened, it is acceptable that a male family member could kill a relative.

It's unclear whether Yahya or Hamed Shafia will be called by the defence to testify, according to the CBC's Daniel Halton.

The three accused, who are from Montreal, each have their own defence lawyers.

The trial will continue this week in Kingston before breaking for the holidays. The defence will resume its case on January 9, and expects to take the whole month of January before resting its case.