A man from Winterport accused of assaulting his girlfriend then getting involved in a standoff with police has pleaded not guilty. 35-year-old Joseph Chekovsky is charged with domestic violence assault and domestic criminal mischief. Police say last month he tried to slash the tires to his girlfriend’s car and smashed a window while she was inside, sending glass into her face.They say Chekovsky then went back into the house with a knife. The woman’s 11-year-old son was inside. About five hours later, Chekovsky surrendered to police. The boy was not hurt.Chekovsky’s trial is scheduled for next month.