Liam McAtasney's attorney, Charles Moriarty, made the claim during a hearing where he unsuccessfully sought to have a judge dismiss a murder indictment against McAtasney.
Moriarty told state Superior Court Judge Richard English that the acquaintance told detectives that McAtasney was "always making things up to be more interesting."
Police say the acquaintance secretly record McAtasney confessing to the crime. Moriarty is seeking to have that recording excluded from evidence at McAtasney's upcoming trial
Monmouth County prosecutors say the 20-year-old Neptune City man killed 19-year-old Sarah Stern on Dec. 2, 2016, during a robbery that netted $10,000.
McAtasney's fiend, Preston Taylor, has said he helped him dump the body.
Stern's body has never been found.
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