@jmc88 - Sometimes the media can blow those types of cases out of proportion and distort the facts. What happened in Ray Lewis's case was something that happens with a lot of murder cases.
They could not connect him to the murder so they did the best they could, made him a witness. Even though they could not connect him, they could put him at the scene and by giving him a plea agreement he could get past felony charges and become a star witness for the prosecution.
It is not unusual for people to testify in these types of cases and receive an obstruction of justice charge. Some legal theorists see this as them knowing something about what happened, but they cannot be proven to commit the act. Usually this shows an admission of guilt they did something wrong but cannot be prosecuted for some reason.
Ray Lewis's case was not unusual and is something that occurs very often and shows how obstruction of justice charges can occur for someone that may have known more then they were letting on.