Obtaining oral evidence is risky. Because people who know the case may have testified to the investigation organ. If there is any contradiction, they have either perjured themselves before or lied later. During the trial, the witness is likely to change his testimony and lie that he was deliberately instigated by the defendant's family or defender to exonerate himself. It is possible to become a "criminal suspect" because of the crime of suspected defenders destroying, falsifying evidence and obstructing testimony.
If you just know the case and see if there is any direction to work hard, it is ok, but it needs the consent of the victim's family.
As the victim's attorney, he usually doesn't discuss the case with the defendant's family, let alone write the case.