A Worcester woman charged four years ago with suffocating her 13-month-old son with a teddy bear has filed a federal lawsuit against the Police Department and officers she says coerced her into confessing. Nga Truong alleges malicious prosecution, false arrest and false imprisonment, intentional infliction of emotional distress, and civil rights violations in her complaint. Truong was 16 when she was accused of killing her son, Khyle, in 2008. She was held for almost three years before prosecutors dismissed a murder charge after a judge ruled that her confession to police was obtained illegally. Police Chief Gary Gemme told the Worcester Telegram & Gazette that the lawsuit lacks merit.