They said Shannon Smith was upset and told them she had been struck in the head, bitten on the face, knocked to the ground and almost suffocated by Deneen when he put his hand over her nose and mouth.
They said Smith had marks and swelling at two places on her head, a bite mark on her cheek, and complained of nausea.
Deputy William Blair said he had to keep her from leaving the scene with her 2-year-old son.
"She said she just wanted to get out of the area," he said.
Blair said Smith showed him marks on her head under her hairline, and told him that Deneen had "learned to beat her where her hair could cover it and nobody would see it."
Blair said the woman was taken to Washington County Hospital for treatment of her injuries.
Smith testified that they had argued, but said Deneen never beat or kicked her. She said the bite mark was from an affectionate "nibble" the night before.
Smith said she didn't tell anyone that Deneen had hit her, and didn't recall having marks on her head. She did recall telling deputies that Deneen knew to hit her on the head, because the marks wouldn't be visible.
Smith said she had known Deneen since the two were in their early teens. "He's my boyfriend," she said. She and her son, who is nicknamed "Lucky," live with Deneen, Smith said.
Deneen did not take the stand.
Deneen is awaiting trial in Washington County Circuit Court on charges he abducted "Lucky" and assaulted Smith in mid-February of this year. He was free on bond on those charges at the time of the June assault, prosecutors said.