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Westminster Police Department, File, Associated Press
FILE - This file booking photo released by the Westminster, Colo., Police Department shows Austin Reed Sigg. Sigg, 18, who has pleaded guilty to the grisly October 2012 slaying of 10-year-old Jessica Ridgeway, will be sentenced during a hearing beginning Monday, Nov. 18, 2013.

GOLDEN, Colo. — A lawyer for a Colorado teen who killed and dismembered a 10-year-old girl says trauma he suffered before and during birth caused him to have deformities.

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A psychologist hired by prosecutors testified Monday during Austin Sigg's sentencing hearing that the 18-year-old had no empathy for Jessica Ridgeway. Psychologist Anna Salter described him as "sadistic" and said his attack was planned, not impulsive.

Defense attorney Katherine Spengler pointed out that Salter only reviewed records provided by prosecutors and didn't know Sigg's mother inhaled paint fumes and fell down stairs before his birth.

She also said Sigg was born with an abnormality in his intestines as well as a head deformity caused by his birth by vacuum extraction.

Sigg faces a possible life prison term. He can't be executed because he was 17 at the time of Jessica's death.