The man convicted of murdering Cornish 13-year-old Caroline Dickinson in France has lodged an appeal.
Montes has offered no new evidence
It is believed Francisco Arce Montes is appealing against both his 30-year jail term and his conviction for murder.
A judge sentenced Montes to 30 years, with the recommendation he should serve at least 20 years, earlier this month, but he may now get a retrial.
The family of Caroline, who was killed eight years ago in a Brittany hostel, said they were "angry and very upset".
BBC Paris correspondent Caroline Wyatt said appeals in France differed greatly from appeals in Britain and Montes, 54, was entitled to almost a full retrial.
She said Montes was not believed to be disputing the evidence as part of his appeal or offering new evidence.
Under French law the defendant does not have to specify legal grounds in order to appeal.
The Dickinson family's outrage was echoed by their local MP, Paul Tyler, who described the appeal as a "cruel and irrational decision".
BBC Paris correspondent Caroline Wyatt says the prosecutor may lodge a counter-appeal and press for a life term over the killing.
Caroline Dickinson's family are outraged
She said the Spaniard's defence team were saying they were "baffled and bewildered".
One of his trial lawyers, Olivier Dersoir, told her: "Arce Montes appealed on his own; in fact, I found out through the press.
"I don't really understand this move. There is always a risk that he will get a higher sentence."
Lives 'on hold'
Caroline's mother Sue, 46, from Launceston, and her 48-year-old father John, from Bodmin, Cornwall, were informed on Monday night that Montes had lodged an appeal.
The family said in a statement: "We are angry and very upset to learn of the appeal that has been lodged and that our wish to begin the process of rebuilding our lives is now, yet again, on hold.
"However our commitment to ensure justice for Caroline remains steadfast and we intend to be present at any retrial when and wherever that may be."
Caroline was murdered by Montes in the early hours of July 18, 1996, as she slept on the floor of a dormitory of a hostel in Pleine Fougeres, Britanny.
The French justice system allows everyone an automatic right to appeal.
The retrial will be at least six months after the original trial but will probably be in eight to 12 months time, French police have said.
It may not be at Rennes but will be within Brittany.
There will be 12 jurors at the retrial and three judges.
It is not clear whether witnesses will have to attend the retrial unless the evidence given in the first trial is questioned.
The trial in Rennes heard there was a billion-to-one chance DNA found at the scene did not belong to Montes.
Jurors rejected his claim that Caroline was still alive when he left her after sexually assaulting her in the French hostel.
During the trial Montes had admitted sexual assault but denied murdering the schoolgirl.
Reports suggest Montes may believe he should have been convicted of rape and manslaughter rather than rape and murder.