An 18-year-old Springfield man, Marcello Scott, is locked behind bars in the Sangamon County Jail after a seven-month-pregnant teenager used a kitchen knife to defend her unborn child during a violent home invasion. The Sangamon County Sheriff's Office confirmed that the expectant mother acted completely in lawful self-defense when she stabbed Scott in the chest after he forcibly breached her apartment threshold and began battering her. The post…