So, why did Robert Fields wait until now to claim that he saw Phylicia after she was reported missing? Her disappearance made national headlines. Even if he didn't know at the time that she had been reported missing, once he did realize it why didn't he immediately notify authorities? It makes no sense that he would suddenly come forward with that information at this stage. Is Fields a friend of Johnson, or a friend of Johnson's friends/relatives?
Fields had better have an exact date, time, location and other details of when he saw Phylicia after her disappearance, or else I think his testimony will mean diddly-squat to the case. It seems unusual, anyway, to name someone as an alibi-witness because he didn't see the accused, unless the witness saw the victim being murdered and knows who the "real" killer is. Phylicia's body has been recovered, so if a witness did see her alive after she was reported missing, she was murdered after the sighting - therefore, the "alibi" is meaningless. How can the witness know that Johnson wasn't with Phylicia when she was murdered? KWIM?