POUGHKEEPSIE, N.Y. — They seemed the picture of love, a handsome couple who doted on their cat, partied with friends at local pubs and paddled the Hudson River in kayaks they stored in their apartment here.

Then, on a Sunday evening in April, Angelika Graswald, 35, made a desperate 911 call from the river. The kayak her fiancé, Vincent Viafore, 46, was in capsized, and she could not find him in the cold water. He is presumed dead.

Ten days later, as she laid flowers in his honor on Bannerman Island, the spot the couple had been visiting the day of Mr. Viafore’s death, the police arrested Ms. Graswald and charged her with second-degree murder. At the time, the police said that after his disappearance, she made a number of conflicting statements that implicated her in his death.

But at a bail hearing in Orange County on Wednesday, prosecutors went further. Julie Mohl, an assistant district attorney, quoted Ms. Graswald — in what sounded more like a confession — saying that she had tampered with Mr. Viafore’s kayak and that it had “felt good knowing he was going to die.”