I believe that Portia had the knowledge of the conspiracy, but was not guilty of Caesar's death. Although Portia knew about the conspiracy, she was not at fault. My opinion suggests that Caesar was responsible for his own murder. No matter what Portia does, Caesar's fate would not be shaken.
             After the conspirators left Brutus' house under hidden faces (Know I these men that come along with you? (2.1.7)), Portia enters the room to find Brutus upset and preoccupied. She begs him to tell her why he is so upset and he tells her that he is sick in the mind, not of the body. She again begs him to tell her what is wrong, asking him, "Think you I am no stronger than my sex, Being so fathered and so husbanded?" (2.1.295-6). Even before Brutus sends Portia away before telling her what she wants to know, Portia was suspicious. You can conclude that she was suspicious since she questioned Brutus about her role as his wife. That maybe the reason why she entered where Brutus was after the conspirators left. Therefor I assume that she was listening to Brutus' conversations and had some knowledge of the conspiracy.
             Portia orders Lucius to go to the Senate House. He asks her what he should do there, but she is so distracted that she couldn't to tell him what to do. She remarks to the audience, "I have a man's mind, but a woman's might. How hard it is for women to keep counsel!" (2.4.7-8). She indirectly says that she knows what Brutus is planning to do to Caesar and doesn't want to keep it a secret. The soothsayer who had warned Caesar sees Portia and informs Portia that he will try to once again warn Caesar about his fate.
             Caesar laid out the foundations of his own death. He refused to listen to the nightmares of his wife, Calpurnia. He also ignored the supernatural omens such as the storm and the events Casca described (Men walkting flames, slaves not burned by fire, etc.). Caesar even believed th
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