Priscilla Lujan was awake soothing her infant son at 10 p.m. and again in the middle of the night. She let him gum one of the salty pistachios she was eating. She mixed a bottle of formula at the side of their shared bed.It was the fitful kind of night that’s easily forgotten after a strong cup of coffee and a shy smile from a sleep-refreshed baby. But that’s not what happened the next morning. When Lujan woke up, her son – not yet 6 months old on Feb. 3, 2012 – was cold. His lips, blue. His eyes, half open. She screamed to her mother to call 911.