ST. PAUL — A lawyer for a Wisconsin man convicted of killing his three daughters has taken the first step in the appeals process.

Attorney Tom Provis filed a notice of appeal Friday. He said he’s looking for legal errors in the case against Aaron Schaffhausen. He says he expects it will be at least three months before the first briefs are filed.

Schaffhausen pleaded guilty to three counts of first-degree intentional homicide but maintained that he was insane when he cut his daughters’ throats at their River Falls, Wisconsin, home in 2012.

After a 12-day trial last year, a jury determined he was sane, a decision that sent him to prison rather than a mental institution. He was sentenced to life without parole.