Van der Sloot, the key suspect in the 2005 disappearance of U.S. teenager Natalee Holloway on the Caribbean island of Aruba, will use a "violent emotion" defense in the slaying of Stephany Flores, attorney Maximo Altez told The Associated Press.

Altez said he filed papers three weeks ago informing prosecutors of his intent to argue that Van der Sloot became enraged and killed the 21-year-old Peruvian business student last May 30 because she had learned of his relation to Holloway by looking in his laptop.

The 23-year-old Dutchman is accused of first-degree murder, which carries a 15- to 35-year sentence on conviction.

The "violent emotion" plea is typically used in Peru for crimes of passion where a spouse, for example, is surprised in the act of adultery.

If it were to be accepted by a trial judge, Van der Sloot would be sentenced to 3 to 5 years, and Altez said his client could be freed in 20 months.

Peruvian judges and prosecutors rarely speak publicly about their cases and it was not known how they would react to Van der Sloot’s planned plea.

A prominent defense lawyer not involved in the case, Mario Amoretti, told the AP that much would rest on how judges received the opinions of psychologists and other experts about the emotional state and history of Van der Sloot.

The lawyer for the victim’s family called the proposed plea absurd, saying that given all the factors of the case, Van der Sloot deserved to spend a minimum of 25 years in prison.

"The manner in which the suspect killed Stephany evidenced disproportionate violence," attorney Edward Alvarez said.

The young woman — who was killed in Van der Sloot’s Lima hotel room five years to the day after Holloway disappeared — was bludgeoned and asphyxiated, according to the coroner’s report.

Alvarez said Van der Sloot also stole money and other items from Flores before fleeing south from the Peruvian capital to Chile, where he was later captured by police.

In a signed confession last year, Van der Sloot described slamming Flores in the face with his right elbow, strangling her for a full minute then taking off his shirt and asphyxiating her. He also contended Flores threw the first blow.

Van der Sloot has admitted, however, to being a congenital liar.

He has several times confessed then recanted a role in the disappearance of Holloway, an 18-year-old Alabama student who was visiting Aruba on a high school graduation trip with classmates when she meet Van der Sloot at a casino.

Because of delays in Peru’s judicial process that Alvarez blamed on the defense, Van der Sloot has not yet been formally charged.

The young Dutchman remains in Lima’s Castro Castro prison, where his lawyer says he gives English lessons to other inmates.

An attorney for Holloway’s mother, Beth Twitty, said she considered the planned plea "outrageous." Twitty knows the Flores family will never accept it and she plans to "make whatever noise she has to" to make sure it doesn’t happen, the lawyer, John Kelly, added.

"He’s a very slippery, smart criminal," Kelly said of Van der Sloot, adding that any suggestion he "flipped out for a moment" in killing Flores was mocked by the meticulous calculation of his attempt to cover up the crime and his escape.

Kelly also emphasized that even if Peruvian justice were to go easy on Van der Sloot he still faces prosecution in the United States on wire fraud and extortion charges.

An Alabama grand jury indicted the Dutchman in June for allegedly trying to extort $250,000 from 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 it is believed he used to travel to Peru.

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Associated Press writer Frank Bajak contributed to this report.