why couldn't mary surratt's son come to safe his mother's life?

In 1865 abraham lincoln and his went to to the theater to see a play but he did not know that john wilks booth was behind him then john wilks booth shot abraham lincoln even his conspiriters one of them was on the run and the men who was on the run was mary surratt's son john surratt jr. and john wilks booth was killed in a barn on the night of the murder of abraham lincoln mary surratt was put on trial and while she was in prison the gaurds came and gave her the verdict and found her guilty of murder and sentenced her to be hanged until she was dead all her son could've done was come to save her life but he did not all he was doing was acting like a coward and and years later he turned himself in but was let go because the peaple did not have enough evidence he could've turned himself in earlier to safe his mother's life but he ended up acting like a coward instead of coming to his home to safe his mother's life and that is the act of a coward and that coward's name was john surratt jr.