A Queensland man accused of murdering his wife and baby daughter has appeared in court as ten witnesses gave evidence about his behaviour leading up to the alleged killings. Matthew James Cox, 34, is accused of stabbing and killing his 30-year-old wife Tayla Black and their 11-week-old daughter Murphy at their Rockhampton home in August 2023. WATCH VIDEO ABOVE: Witnesses testify in trial of man accused of murdering wife and baby daughterKnow the news with the 7NEWS app: Download today ArrowDays after the alleged murders, Cox turned himself in to a Brisbane police station. Credit: SuppliedCox’s lawyer is now arguing his mental health makes him unfit to stand trial. His manager at the time, Mitchell Harris, said he knew “two different Matts — pre-admission into the mental health system and post-admission.”