By Debbie Emery - Breaking Celebrity News Reporter

Just a week after he pleaded guilty to the murder of Stephany Flores, convicted killer Joran van der Sloot is appealing his 28-year prison sentence, according to his Peruvian lawyer.

Attorney Jose Luis Jimenez claims that the three judges who sentenced van der Sloot on January 13 did not take into account his prior confession to the May 2010 murder of the 21-year-old Peruvian student, reported USAToday.com.

The appeal was reportedly made last week and comes in light of Breaking Celebrity News's exclusive report that Jimenez claims the 24-year-old Dutchman is upset with him for returning almost $75,000 that Florida woman, Joran’s “guardian angel” Mary Hamer sent him for "bail."

"That upset him very much and he saw me as a traitor," wrote Jimenez in an e-mail to Breaking Celebrity News.

He claims that it was Joran's decision to ask Mary for the money, and that he simply verified that it went into his account.