The scene from The Crucible by Arthur Miller to which you refer happens in act three of the play and is also the turning point (crisis/climax) of the story.
John Proctor has gone to the court to tell them what he knows to be true: the girls, led by Abigail Williams, are lying. Even worse, they are lying for personal gain. In Abigail's case, the gain is Proctor. The two of them had an affair which she obviously wants to continue but which Proctor does not. Abigail has accused Elizabeth Proctor of witchcraft, hoping that Proctor will turn to her once his wife is dead.
Proctor has been hesitant to speak before now, knowing that his testimony will lose him both his reputation and his life, for lechery is a hanging offense. He does finally confess, and of course Abigail denies the charge. To settle the matter, Judge Danforth sends for Elizabeth, since Proctor has made it clear that Elizabeth is aware of the affair and she never lies.
The answer to your question is found primarily in stage directions. Elizabeth arrives at the courthouse and stands at the door until she is admitted into the courtroom.
There is a knock. He [Danforth] calls to the door. Hold! To Abigail: Turn your back. Turn your back. To Proctor: Do likewise. Both turn their backs - Abigail with indignant slowness. Now let neither of you turn to face Goody Proctor. No one in this room is to speak one word, or raise a gesture aye or nay.
He turns toward the door, calls: Enter! The door opens. Elizabeth enters with Parris. Parris leaves her. She stands alone, her eyes looking for Proctor.
When Elizabeth enters the room, both Proctor and Abigail are facing the front of the room, with their backs to the door (facing the same direction as Elizabeth). She desperately wants to see her husband's face, but she is unable to do so. All she sees is their backs. What follows is one of the great tragic moments in literature.