If convicted, the accused could be held in a juvenile jail until they turn 21.
The case, which spread from social media to the national mainstream media, has sharply divided the small town.
The alleged victim and two other witnesses from her home state of West Virginia are expected to be called to testify, a defence official said on the eve of the trial.
On Wednesday, prosecutor Marianne Hemmeter told Judge Thomas Lipps, who is hearing the case without a jury, that the girl was “somebody who was too impaired to say no, somebody who was too impaired to say stop”.
“This case hinges on their exploitation of their knowledge of that impairment.”
The family wants this matter over so they can move on with their lives and their daughter’s healing.
She argued that the defendants were aware of the 16-year-old’s state and took advantage of it throughout the evening of the alleged attack.
A defence lawyer for Trenton Mays said his client “did not rape the young lady in question”. Mr Richmond’s lawyer made no opening statement.
Mr Mays, the team quarterback, and Mr Richmond, a wide receiver, were arrested some 10 days after the alleged attack.
Prosecutors say the girl was attacked twice after the party while intoxicated beyond the point of consent, first in the back seat of a moving car and then in the basement of a house.
Witnesses said the girl was so drunk that she vomited at least twice and had trouble walking and speaking.
In an excerpt of a videotaped interview with the ABC News programme 20/20, Mr Richmond said the photo of the girl being carried out of a house by him and his co-accused was a joke. He contends the girl was awake.
But the alleged victim’s civil lawyer, Bob Fitzsimmons, said those claims were “bizarre”.
“The family wants this matter over so they can move on with their lives and their daughter’s healing,” he told the Associated Press.
Three other students who witnessed the alleged attack were not charged. Those witnesses include two who took a video and photograph, then deleted the images.
The Ohio attorney general’s office told lawyers for those students last autumn that if the images had been found, they would have been charged.
The case, which has fiercely divided the town, was thrust into the national spotlight amid interest by bloggers and the hacker activist group Anonymous.
A video originally posted on YouTube emerged in August of a student joking about the alleged rape and referring to the girl as “dead”.
Some claimed that the community had sought to cover up a crime in order protect the two accused.
A blogger, Alexandra Goddard, received threats after she named the alleged attackers, posting messages on Twitter and an image taken on the night of the incident.
Steubenville officials say outsiders have unfairly criticised the police’s handling of the case.
They have created a website, attempting to refute a number of allegations, including that the local police department was full of ex-football players who played on the Steubenville high school team.
Reprinted from BBC