Justice Brewer said it was clear the pair did not get on.
On the day Mr Tiatia was killed, the pair had got into an argument and it was clear that Langley had "had enough".
"You went upstairs and you got the knife. Your partner tried to talk you out of it but you headed downstairs with the knife intending at least to confront Mr Tiatia," Justice Brewer said.
Langley stabbed Mr Tiatia twice, and while each was a deep wound, one was fatal.
"I find that when you stabbed Mr Tiatia, not once but twice, you intended to hurt him badly, and you knew as you stabbed him that you might very well kill him, but you stabbed anyway."
Justice Brewer said despite the fact Langley was only 19 when he committed the crime and had no history of violent offending, he had no choice but to impose a life sentence.
"I could point to the fact that you still deny the offence and point to the fact that you committed it having refused to listen to your partner's pleas to stay upstairs with her.
"I could point to the fact that after you stabbed Mr Tiatia you made no effort to help him but just left straight away. But I do not need to."