also revealed the Abigail is lying when she admits to John Proctor in private that Betty's "illness" is simply pretense and that she is not bewitched. Abigail tells him that they were just dancing in the forest and were frightened when her uncle saw them. After Reverend Hale begins to question Abigail, she uses Tituba as a scapegoat by placing the blame on her. Abigail then witnesses Tituba accuse two women of witchcraft to avoid execution and begins falsely accusing numerous citizens to distract from her own transgressions. It also becomes evident that Abigail is lying when Mary Warren insists that she stuck the needle into the poppet while Abigail watched, which means that Abigail is manipulating the court officials in order to kill Elizabeth Proctor. Abigail also lies when she denies having an affair with John Proctor. In Act One, Abigail speaks to John and it is revealed that they have had relations in the past. Therefore, her denial in act three is an obvious lie. The fact that Abigail steals her uncle's life savings and flees the community indicates that she was lying the entire time.

We know from the outset that Abigail is lying because she acknowledges her deceit when she creates it, telling the others to go along with her. 

At the play's opening, Betty Parris is pretending to be sick because she is worried about the punishment that will be inflicted on her and her friends for being discovered dancing naked in the woods. 

Abigail takes control of the situation by deflecting attention to others. She does this, however, only after the audience is clearly informed that Abigail had been drinking blood in the forest and performing rites of "witchcraft" as the town sees it. 

To protect the group from punishment for what they have done and what she has done herself, Abigail insists that the group maintain a lie. 

...she forcefully insists that the girls stick to the story that they were only dancing and that Tituba and Ruth alone conjured her dead sisters.

In the next scene, Abigail denies the truth that has just been clearly revealed when she tells Proctor that the witchcraft accusations are nonsense. She tells him that the girls were merely dancing in the woods. 

This scenario offers clear evidence from the outset that Abigail is lying. Additionally, in the first scene she lies about why she was fired from the Proctor home (her story is shown to be a lie in the second scene). She lies also about Elizabeth Proctor's poppet. This lie is recognized immediately by the audience for what it is - a deception intended to incriminate Elizabeth.

When Ezekiel Cheever finds the needle stuck into the poppet's belly, he says, 

Why, this go hard with her, Proctor, this—I had my doubts, Proctor, but here's calamity. 

To the courts, the fact that a doll is found in Elizabeth Proctor's house with a needle stuck into its belly when Abigail has seemed to suffer the same affliction, is proof enough of Elizabeth's guilt. This is why he calls it "calamity." Abigail claims that Elizabeth sent her spirit out to push the needle into Abigail's stomach while she sat at dinner. This evidence is called spectral evidence: when, the Puritans believed, a witch would send out her specter, or spirit, to do her bidding while her physical body exists elsewhere. It was decided that the court would accept spectral evidence. This evidence alone was enough to convict some witches because, as Danforth says, no one can see the witch's specter besides the victim and the witch herself. This spectral evidence, the incriminating poppet, and Abigail's testimony regarding each, is plenty of evidence to convict Elizabeth.

In Act II, Cheever comes to the Proctor household to investigate Elizabeth.  He has a warrant to check the house for poppets (homemade dolls).  Elizabeth is confused since she says she "has never kept no poppets, not since I were a girl."

Cheever tells the Proctors that Abigail came to dinner that evening with a needle stuck in her belly.  Abigail has told the court that Elizabeth Proctor sent her spirit out that night and stabbed her.  Cheever and Hale feel that they have the necessary proof, when they see a poppet on the mantel and find a needle hidden inside.

The audience knows that Mary Warren made the poppet and gave it to Elizabeth in scene 2.  Mary Warren tells Hale that she made the poppet and kept the needle inside for safe keeping.  She even points out that Abigail saw he do this, and so should know.

We see here that the courts are not interested solely in the truth.  Even when Mary Warren admits that the poppet is hers, Hale doubts her honesty.

Child, are you certain this be your natural memory? May it be, perhaps, that someone conjures you, even now, to say this?

When Ezekiel Cheever arrives at the Proctors' home to arrest Elizabeth, he collects the poppet—a small rag doll—that Mary Warren made for Elizabeth in court that day. He lifts the doll's skirts and finds a needle stuck deeply into the middle. He goes on to tell the court the following:

[Abigail Williams] sat down to dinner in Reverend Parris's house tonight, and without word nor warnin' she falls to the floor. Like a struck beast, he says, and screamed a scream that a bull would weep to hear. And he goes to save her, and, stuck two inches in the flesh of her belly, he draw a needle out. And demandin' of her how she come to be so stabbed, she . . . testify it were your wife's familiar spirit pushed it in.

Despite John Proctor's protests that Abigail clearly stuck the needle into her own stomach and that this is not proof of Elizabeth's guilt at all, both Reverend Hale and Cheever seem to think of it as absolute evidence.

Something called spectral evidence was allowed during the Salem Witch Trials. Spectral evidence could only be offered by the afflicted, a witch's victim, and it consisted of the victim's testimony that he or she was visited and harmed by the witch's specter or spirit or the specter of her animal familiar. (When Abigail claims in act 3 that Mary Warren is sending out her spirit as a yellow bird, she is providing spectral evidence against Mary, and this is why Mary gets so scared.)

Even when Mary explains that she stuck the needle into the poppet herself for safekeeping and that Abigail saw her do it, it makes no difference. When Elizabeth, realizing Abigail's treachery, says, "The girl is murder! She must be ripped out of the world!" Cheever considers this to be evidence against her as well. She has appeared to threaten Abigail, who is believed by the town to be entirely truthful.

The main piece of evidence that is used to back up Abigail Williams's claim that Elizabeth Proctor is a witch is the "poppet" that is found in Proctor's home.  This is a doll that Proctor has allegedly been using like a voodoo doll.

Abby says that Proctor has used the doll to bewitch her.  She screams with pain and says that Proctor has done something to make her stomach hurt.  When the men go and find the poppet and Proctor's home (it was put there by Mary Warren) they find it has a needle stuck in its stomach.  This is the proof they need to arrest Proctor.

In The Crucible, Abigail Williams is a young girl, who is bent on revenge. We know that she is accusing many of the women in town of practicing witchcraft. Her main goal is to get rid of Elizabeth Proctor. Abigail had worked in the Proctor house as a servant. Abigail ended up having an affair with Elizabeth's husband, John, and Elizabeth finds out and fires Abigail. This makes Abigail want to get back at Elizabeth. Abigail's affair with John Proctor has fueled her anger.

"I look for John Proctor that took me from my sleep and put knowledge in my heart! I never knew what pretense Salem was, I never knew the lying lessons I was taught by all these Christian women and their covenanted men! And now you bid me tear the light out of my eyes? I will not. I can not! You loved me, John Proctor, and whatever sin it is, you love me yet."

Abigail gives Mary Warren a poppet, a doll, to take home with her. Mary is now working as a servant for the Proctors. Abigail complains at dinner that she is not feeling well, and grabs her stomach in pain. This is the event that has led them to search the Proctor's home. They ask Elizabeth if she has any dolls lying around and she says no, but they find the poppet with a needle stuck in its belly. This is what leads to Elizabeth's arrest and conviction of witchcraft. Mary Warren was a very timid girl, who was easily influenced. Abigail brought her into her group of friends, knowing that she could control Mary. 

What is tragic is that because of a young girl, who was infatuated with a man, accused innocent women of something that would lead to their deaths. Yes, John Proctor had an affair with Abigail, but Abigail is the one who made false claims. 

There are two answers to this question, the first occurring near the end of act two.  In this act, Elizabeth is arrested after they find a poppet (a doll) in her house that has a needle stuck into its belly.  Coincidentally, just that evening, Abigail fell

"to the floor...and screamed a scream that a bull would weep to hear...and, stuck two inches in the flesh of her belly, he draw a needle out.  And demandin' of her how she came to be so stabbed, she testify it were [Elizabeth]'s familiar spirit pushed it in."

So, to summarize, Abby pulled a needle out of her belly and claimed that Elizabeth's witch of a spirit stabbed her with it, through the use of some sort of voodoo doll.  So, when they went to Elizabeth's house and found the poppet with the needle, they felt that it was "hard proof" of Elizabeth's guilt.  Never mind that Mary Warren said that she was the one who stuck the needle in the doll and that "Abby sat beside" her when she made it, and most likely saw her put the needle there.  No, such logical facts hold no sway in this situation, and Elizabeth is arrested and jailed.

Later, near the end of act three, John confesses to adultery, and Abby denies it.  So, Danforth brings in Elizabeth to ask her if her husband is guilty of adultery.  She tells an understandable lie and says that no, he isn't.  Her denial of the adultery further support's Abby's innocence, and she is able to gain control of the courts once again.

I hope that helps a bit; good luck!

Abigail Williams gets help from Mary Warren in setting up the accusation and evidence against Elizabeth Proctor in The Crucible. 

Mary Warren has been attending the court sessions daily and one day she is given a doll, a poppet, to bring home with her. Abigail Williams is the one who gives this doll to Mary Warren, who takes the doll to the Proctor house. 

When the deputy comes to arrest Elizabeth he asks if Elizabeth keeps dolls in the house. He discovers the doll and examines it, finding a needle stuck into the belly of the doll. The deputy then tells the story of what "happened" to Abigail Williams as she was eating dinner. Abigail clutched her stomach and began to writhe in pain saying that someone was stabbing her. This led to the deputy's visit, prompted the search for the doll, and was used as evidence against Elizabeth. 

At the end of Act II of "The Crucible", Elizabeth Proctor is taken away by Cheever because she has been accused of witchcraft by Abigail Williams. According to Cheever, when Abigail had been eating dinner with the judges and other magistrates of the Salem courts, Abigail pulled a long needle out of her stomach, claiming that Elizabeth had sent her spirit to stab her with it. Abigail claimed that Elizabeth had a poppet that she used almost as a “voodoo doll” and that they would find a needle in the doll exactly where the needle was in Abigail’s stomach. The doll had actually been made by Mary Warren in court, and Abigail had seen Mary stick the needle in the doll so that she would not lose it.