Van Der Sloot said he killed Stephany Flores, whom he met at a Lima casino, after she used his computer and discovered his connection to Holloway's disappearance. Police said a study of his computer proves that is not true.
"She didn't view anything about Holloway. It's a lie that she tried to ask him about (the case)," the technology chief of Peru's police, Col. Oscar Gonzales, told The Associated Press.
"We deny the colonel's claim," Van der Sloot's attorney, Maximo Altez, told the AP of Gonzales. "We will be presenting our own expert analysis regarding the laptop."
He is charged in Peru with the first-degree murder of Flores last May. Altez said he plans to plead guilty by reason of insanity, which is called "violent emotion" in Peruvian law, arguing that he became enraged after she looked in his laptop and learned of his relation to Holloway.
If the plea of insanity is accepted, that would significantly shorten his sentence as he could plead guilty to manslaughter.
First-degree murder carries a 15 to 35-year sentence in Peru. Manslaughter could bring three to five years.
The young Dutchman remains the key suspect in the unsolved 2005 disappearance of Holloway, an 18-year-old Alabama student he met in a casino on the Caribbean island of Aruba.
Van der Sloot was indicted last June in Alabama on federal wire fraud and extortion charges for allegedly trying to extort $250,000 from Holloway's mother, Beth Twitty, in exchange for information on where she could find her daughter's body.
According to court papers, Van der Sloot received a total of $25,000 a few weeks before Flores' death, money that investigators have said they believed he used to travel to Peru.
The Associated Press contributed to this story