A man who admitted the cold case murder of teenager Michelle Bright did so falsely because he is unsophisticated and vulnerable to manipulation, a jury has heard.
Craig Rumsby, 56, confessed to undercover police he killed the 17-year-old more than 20 years ago because he was caught in a "ruse", his barrister Nicholas Broadbent told a NSW Supreme Court jury.
In his closing address, Mr Broadbent described how officers offered up details to Rumsby in a trick designed to extract admissions from him.
The admissions could not be trusted, Mr Broadbent argued.
Rumsby initially denied involvement in the killing, but over time changed his story under "sustained pressure".
When he did confess to the murder, the details he gave contradicted crime scene evidence unless they were first suggested to him, the jury heard.
Parallel to the covert police operation, Rumsby was entangled in a romance scam, in which he believed he was in a relationship with an American woman who promised to come to Australia and buy the pair a house.
"(This) tells you a lot about Mr Rumsby," Mr Broadbent said at Dubbo Courthouse on Wednesday.
"About his vulnerability to manipulation; his gullibility and his willingness to accept the farfetched where he perceives a benefit; his lack of sophistication; his ability to consider risk against reward."
He had little in the way of familial or social support and was struggling financially, heightening his susceptibility to inducement, the jury heard.
Rumsby is accused of murdering Ms Bright after she left a friend's 15th birthday party in Gulgong, central west NSW in the early hours of February 27, 1999.
No physical evidence has been found linking him to the scene, despite him volunteering multiple DNA samples.
Rumsby is also charged with an assault on another 18-year-old woman after she left a New Year's Eve party on January 1, 1998. He is alleged to have choked her with the intent of raping her.
He has pleaded not guilty to both charges.
Mr Broadbent questioned the reliability of the alleged assault victim's evidence given to court, saying it differed from statements and photographic records taken on the day of her attack.
In the contemporaneous records there is no mention of blood on the woman's face or that the assailant removed her underwear - evidence that she gave to the court over 20 years later.
The jury heard earlier in the trial the woman, who cannot be named, did not press charges against Rumsby and retracted a statement she made at the time as she feared going to court and having her character discredited.
Crown prosecutor Lee Carr SC on Tuesday argued Rumsby's admissions to undercover police prove his guilt in both offences beyond reasonable doubt.
"The accused had a particular state of mind, that being a sexual interest in females, including strangers, in their late teens," he said.
"He had a tendency to act on that state of mind by committing sexual violence on them opportunistically."
The similarity of both offences - in terms of the time, location and manner of the attacks - would make it "extraordinary in the extreme" if they were by sheer coincidence committed by different perpetrators, he said.
The defence is due to wrap up its closing submissions on Thursday.
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