Romeo and Juliet; Fault.

In William Shakespeare's play, Romeo and Juliet, one of the main characters, Juliet, commits suicide near the end of the play. Friar Lawrence is directly responsible for the death of Juliet in all ways. He makes not only one, but three mistakes that all lead to Juliet's death. He gave a poison to Juliet, he trusted someone else with a letter of great significance to deliver to Romeo, and he fled when Juliet was in the most danger at the tomb. Had he not have made these three major terrible mistakes, Juliet might not have killed herself.
Friar Lawrence made a major mistake that he could have avoided himself. He trusted Juliet, an unstable teenage girl, with a fake-death poison. This rash decision was a very poor choice on the friar's behalf. Here, the friar shows his irresponsibility by saying, "If... thou hast the strength of will to slay thyself... take thou this vial... no warmth, no breath shall testify thou livest;" (4.1.72, 93, 98) Friar Lawrence's idea for Juliet is very risky and he should have known better than to try it. Because of what happens, everyone thinks Juliet is dead and shortly thereafter, she is buried alive. This quote shows the true meaning of responsibility, because when he says this, her life rests in his hands. Capulet is even foiled by the plan, because when he says her faking her death, he said, "Death lies on her like an untimely frost." (4.5.28) The fake death has fooled Capulet, Juliet's father, and the rest of the family. Had Friar Lawrence not have given Juliet the poison, she would have never been put in the position that she was in, which eventually leads to her death.
Trusting Friar John to send the letter, and not even telling him that the letter was urgent, was Friar Lawrence's next big mistake. The mistake of him sending someone else to do it was inexcusable; a matter as important as faking death should be dealt with personally. Had Friar Lawrence have personally delivered the letter, the plan might have gone smoothly. Friar John shows his incompetence in the fifth act when he says "I could not send it - here it is again -" (5.2.14). Showing Friar Lawrence's poor decision making again, this quote perfectly shows how Friar Lawrence is responsible for Juliet's death by choosing to send the letter instead of delivering it. At that, he should not have trusted someone as mediocre as Friar John. "The letter was not nice but full of charge, of dear import, and the neglecting it may do much danger." (5.2.18-20) Friar Lawrence trusted a complete buffoon at the most crucial of times and the price was paid for the actions of both friars. Consequently, Juliet dies because Friar Lawrence did not think through that something might arise and a situation this urgent must be dealt with personally. Friar Lawrence could have easily avoided the situation.
Cowardice, plain and simple, was also another reason why Friar Lawrence was responsible for Juliet's death. He runs away when Juliet needs him the most, and in leaving her alone, she kills herself. In the tomb scene, Friar Lawrence attempt's to help Juliet before running away. "(Friar Lawrence): Stay not to question, for the Watch is coming. Come go, good Juliet, I dare no longer stay. (Juliet): Go get thee hence, for I will not away." Friar Lawrence puts himself before Juliet, and worries about getting caught by the watch. He leaves Juliet when she needs him most. Friar Lawrence shows here that he really does not care about Juliet, and that he is very self-centered. He leaves her to kill herself, even though it is entirely his fault that she is even in that situation. Had the friar not have left the tomb, then Juliet might not have had the opportunity to kill herself, as you can see she does in the following quote. "Yea, noise? Then I'll be brief. O happy dagger, [taking Romeo's dagger.] this is thy sheath; [stabs herself.]" (5.3.169) Juliet says these final words before killing herself. We see here what results directly from Friar Lawrence leaving the scene when he should have stayed. Had he stayed, he could have at least attempted to wrench the dagger from her hand, or comforted her until she let go of the knife. Instead of staying to help he chose to run away from the watchmen for his own safety, and because of this final, terrible choice, Juliet ends up dead.
Friar Lawrence makes many bad choices throughout the play; choices that are inexcusable. When he made such terrible choices, he inevitably doomed Juliet to her death. His irresponsible choices, trusting Juliet with poison, giving the letter to Friar John, and running away at the tomb, were awful choices. He consistently shows that he is an awful decision maker, and he is entirely responsible for Juliet's death. One could even say he is more responsible for the death than Juliet herself.