Criminal law — Driving under influence — Search and seizure — Vehicle stop — Unsignalled lane change that did not affect other traffic give rise to reasonable suspicion justifying stop — Request for defendant to perform field sobriety exercises based solely on hint of alcohol on his breath was unlawful — Stop and arrest were unlawful where neither defendant’s driving pattern, hint of alcohol on his breath, nor performance on field sobriety exercises rose to level of demonstrating that defendant was impaired — Motion to suppress is granted