FORT LAUDERDALE, Fla. (AP) — Attorneys for Florida school shooter Nikolas Cruz began building their argument Monday that his birth mother’s alcohol abuse left him with severe behavioral problems that eventually led to his 2018 murder of 17 people at Parkland’s Marjory Stoneman Douglas High School.

Paul Connor, a Seattle-area neuropsychologist, said medical records and testimony by prior witnesses show that Brenda Woodard drank and used cocaine throughout much of her pregnancy before Cruz’s birth in 1998. Woodard, a Fort Lauderdale prostitute, gave up the baby immediately after to his adoptive parents, Lynda and Roger Cruz. Woodard died last year.

Connor, testifying by Zoom, told jurors that people with fetal alcohol spectrum disorder show at a young age problems with motor skills, impulse control, socializing and paying attention — problems previous defense testimony showed Cruz had.

Cruz’s preschool teachers testified he couldn’t run without falling or use utensils. He was diagnosed with attention deficit hyperactivity disorder as a young child and teachers testified that he was extremely anxious and had trouble making friends.

At 5, tests showed Cruz had impairments in 10 intellectual categories including memory, reasoning, language and impulsivity, Connor said. Court records and earlier testimony showed he would have frequent outbursts in class and at home. By middle school, he was making threats.

Connor said he measured Cruz’s IQ at 83, which he said matches the slightly below average intelligence many people with fetal alcohol issues often score. He said IQ tests conducted throughout Cruz’s life found similar results, including one done recently by a prosecution expert.

Under cross-examination by lead prosecutor Mike Satz, Connor conceded he is not board certified in his field but said such certification is voluntary and only a state license is required to practice. He also conceded that he almost always testifies on behalf of the defense in fetal alcohol cases, not prosecutors. He will continue testifying Tuesday.

Cruz, 23, pleaded guilty in October to murdering 14 students and three staff members and wounding 17 others as he stalked a three-story classroom building with an AR-15-style semiautomatic rifle on Valentine’s Day 2018. His trial is only to decide whether the former Stoneman Douglas student is sentenced to death or life without parole. For the seven-man, five-woman jury to impose a death sentence, the vote must be unanimous.

Satz finished his primary case last month. He played security videos of the shooting and showed the rifle Cruz used. Teachers and students testified about watching others die. He showed graphic autopsy and crime scene photos and took jurors to the fenced-off building, which remains blood-stained and bullet-pocked. Parents and spouses gave tearful and angry statements about their loss.

In an attempt to counter that, assistant public defender Melisa McNeill and her team have made Cruz’s history their case’s centerpiece, hoping at least one juror will vote for life.

After the defense concludes its case in the coming weeks, the prosecution will present a rebuttal case before the jury’s deliberations begin.