man accused of helping former lover kill woman during a sexual encounter .
micheal john duffy pleaded not guilty to murdering colleen deborah ayers .
the court heard he strangled ms ayers , 33 , with ` ringleader ' rachel evans .
he said his co-accused evans was the one with a ` twisted desire to kill '
duffy reportedly buried ms ayers in shallow grave on her parents property .
evans pleaded guilty to murder and is set to receive a reduced sentence for giving evidence in duffy 's continuing trial .