Joran van der Sloot's attorney on Wednesday filed an appeal to a ruling that upheld his confession and detention in the death of a Peruvian woman, his attorney said.
Attorney Maximo Altez filed the appeal in the morning, he said.
Ricardo Flores, the father of murder victim Stephany Flores, was also expected to appear before a judge Wednesday to give a formal statement, family members told CNN.
Van der Sloot earlier this month refused an opportunity to give the judge a statement.
Flores will meet Judge Carlos Morales Cordova in Lima, Peru.
As the presiding judge, Morales has the duty to be the chief fact-finder, legal experts told CNN. Morales is getting statements from other potential witnesses, as well.
For his part, van der Sloot is trying to slow down the legal process by appealing his incarceration and trying to nullify a confession he gave.
One judge already denied his claim, but van der Sloot's attorney said his client will fight all the way to the Peruvian Supreme Court and international courts, if necessary. Wednesday's appeal was the first step.
CNN's Jean Casarez contributed to this report.