FARMINGTON — A jury deliberated for a little more than an hour Tuesday before convicting Ramon Martinez of sexually assaulting a 4-year-old girl.

Martinez, 54, will be sentenced to 18 years in prison, Chief Deputy District Attorney Dustin O'Brien said.

O'Brien showed a picture of the girl to the jurors during his closing argument, and he reminded them of her testimony on Monday.

"It's time he take responsibility," O'Brien said. "Find him guilty of what she said he did."

Stephen Taylor, Martinez's attorney, told the jury there was little physical evidence other than a young girl's memory.

He asked them not to convict solely based on the heart-wrenching testimony of a child.

"It's the criminal justice system, not the criminal victim system," he said. "This could happen to anybody. Anybody could be accused of doing something to a child."

The girl was assaulted at Martinez's house in September 2011 while her mother smoked methamphetamine in a nearby bedroom.

She awoke during the assault and ran to her mother and told her about it.

The mother did not notify police but the girl told other relatives, who reported it.

Prosecutors said Martinez chose to assault the girl because the mother was a meth addict and unlikely to go to police.

O'Brien said the girl's persistence in telling other adults proved she was telling the truth.

"The only thing that got this reported was the tenacity of the little girl," he said.