Immediately after the deaths of Romeo, Juliet, and Paris, Friar Lawrence, Prince Escalus considers Friar Lawrence one of the "parties of suspicion." Balthsar, who was Romeo's servant and friend, and the "boy" of Count Paris are also found nearby.
Although Prince Escalus does not verbalize and accusation of guilt, Friar Lawrence declares that he is "the greatest, able to do least" regarding the deaths. He also states that the is there to "impeach and purge, myself condemned and myself excused." In other words, he considers himself guilty, yet innocent; he did play an undeniable role in the tragedies that took place, but he intended only good (peace between the Montague and Capulet families).
Friar Lawrence concludes his monologue recounting the facts of the events that took place by saying
...and if aught in this
Miscarried by my fault, let my old life
Be sacrificed some hour before his time
Unto the rigor of severest law.
The Friar accepts guilt for taking part in the unsuccessful plan and offers to pay with his life, if necessary.
He gave her the means to "kill" herself.