A young father described to a Riverhead courtroom Tuesday how his infant daughter's cries provoked him to hit and shake her until her brain bled. Then another set of cries broke out in court.

The child's mother, Alicia Biondo, 18, doubled over in her seat and let loose piercing sobs as her former boyfriend detailed what he'd done.

Joshua Cohen, 22, of Mastic, pleaded guilty Tuesday to first-degree assault in a deal that will put him in prison for 16 years - nine years short of the crime's maximum sentence. But first, Cohen laid out what happened when Evelynn, just 12 weeks old, roused him from a nap on June 24, 2007:

Cohen said he elbowed the girl off a mattress, then heard her body clank against the bed's metal frame below.

"As she lay on the floor at this point, did you hear Evelynn begin to cry?," Assistant District Attorney Todd Pettigrew asked him.

"Yes," Cohen said. Next, Cohen admitted he kicked Evelynn, then snatched her from the floor, violently jerking her to and fro.

"When you shook her back and forth, did you see her head go back and forth?" Pettigrew asked.

Cohen, lanky, unshaven and dressed in green jail scrubs, bowed his head. "Yes," he said.

As court officers led Cohen to jail, Anthony Biondo, 42, Evelynn's maternal grandfather, shouted, "Back to your cage, you filthy animal!"

Outside court, Evelynn's mother, now a senior at William Floyd High School, said she was glad to see the case conclude, but she still found the court appearance difficult.

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"I'm definitely in a lot of pain," said Alicia Biondo, wiping away mascara smeared by crying. "It made me relive everything that happened that day when I found out what he did to her."

After the assault, Evelynn spent 13 days in Stony Brook University Medical Center. Prosecutors said she suffered bleeding inside her brain and tearing and hemorrhaging in her retinas.

Now nearly 2 years old, Evelynn still suffers daily seizures and has lost her vision as a result of the injuries, said her grandmother, Michelle Waltz, 38, Alicia Biondo's mother.

Cohen's lawyer, Robert Kronenberg, of Hauppauge, said his client has the mental capacity of a school-age child and does not fully appreciate the gravity of what he has done. Nevertheless, Kronenberg added, Cohen is sorry.

"He understands how sad it is that his daughter is hurt and he wishes he could take it back," Kronenberg said. "What you have here is someone who is childlike having a child - I should say two children having a child - with tragic results."

Pettigrew said Cohen's lawyers couldn't prove he lacked the mental capacity to distinguish right from wrong because it simply wasn't true.

"He understood everything that he did," Pettigrew said.

Suffolk County Court Judge C. Randall Hinrichs will impose sentence April 7.