FORT LAUDERDALE, Fla. — A defense lawyer on Tuesday urged jurors to spare the life of Nikolas Cruz, the gunman who murdered 14 students and three staff members at a Parkland high school, saying he was “doomed from the womb” because his birth mother drank heavily and smoked crack cocaine while pregnant. Jurors heard the plea for mercy after nearly three months of trial for Cruz, 24, who last year pleaded guilty to committing Florida’s deadliest school shooting. The Broward Public Defender’s Office argued that Cruz suffered from fetal-alcohol spectrum disorder caused by his hard-drinking, drug-a…