Glynn said the sexually explicit texts showed they intended to continue their relationship when he arrived in Brisbane, despite the fact she told friends otherwise.
"How can you rely on anything she says when she is capable of such blatant lies?" he asked the jury to consider.
Glynn also questioned the evidence Boyce's husband Graham Boyce gave during the trial.
Glynn asked how a man who claimed to have a "sound" relationship with his wife could post "crash slut" on her Facebook page after he learned she was travelling to New Zealand.
"That is about as offensive and disgraceful a message as a man could send to his wife, whatever she had done to anger him," he said.
The jury was also read an email from Boyce to her husband in the month before she died where she said she wanted a divorce, despite Boyce's evidence it hadn't been discussed.
"What of his evidence can you trust?" he asked.
"Graham Boyce is not a witness to who you can give any credibility."
Glynn urged the jury to take into account Lang was questioned for up to 19 hours by police after Boyce died, when he was "in shock and obviously distressed".
Boyce was discovered in her bed on the morning of October 22 with a knife embedded so deeply in her stomach that part of the hilt was inside her body.
Crown prosecutor David Meredith told the jury at the start of the trial they must decide whether the socialite, who had a history of bipolar disorder, took her own life or if she was killed by Lang in a "jealous rage".
- NZN
