In a sworn complaint, Officer Giambra said Mr. Peltomaa was “an emotionally disturbed person” who “indicated that he was willing to be placed in handcuffs for his protection.” But, the complaint said, when the officer tried to “place Mr. Peltomaa in handcuffs to restrain and protect him,” the physics professor fought back, kicking the officer in the groin and shins. The officer said Ms. LaFont then pulled on his arm for a full minute, yelling “Get off him!”

Officer Giambra and his commanding officer, Capt. Michael Falcon, did not return telephone messages on Thursday. The Manhattan district attorney’s office declined to comment on the judge’s decision.

Mr. Peltomaa denies he ever fought with Officer Giambra, though he recalls being confused about why he needed handcuffs to go the hospital. After he was cuffed, he said, the officer shoved him down face first on the tile floor, splitting open his chin and dislocating his thumb.

Then the officers flipped Mr. Peltomaa over, grabbed him by his clothes and dragged him to the ambulance. Ms. LaFont said she was taken to the precinct and put in a squalid cell. Officer Giambra, munching a candy bar, told her Mr. Peltomaa was fine and would be home before she would. “He said he needed to teach me the lesson that you are never allowed to touch a police officer,” she recalled.

Mr. Peltomaa would spend two days in St. Luke’s-Roosevelt Hospital Center with five stitches in his chin and electronic monitors keeping tabs on his ailing heart.

Nineteen hours after her arrest, Ms. LaFont was brought before a judge in Manhattan Criminal Court to face charges of obstructing governmental administration and harassment. The prosecutor on duty offered her a common deal for people who have tussles with the police: plead guilty to disorderly conduct and be released with a penalty of “time served.”

Ms. LaFont refused. “I didn’t believe I did anything wrong,” she said. Over the next months, she also turned down offers from prosecutors to drop the charges in return for meeting certain conditions. What she wanted, she said, was exoneration.