article_snippet: Thomas Martin, a veteran crime scene investigator and president of Crime Scene Forensics LLC, said Thomas Martin, a veteran crime scene investigator and president of Crime Scene Forensics LLC knew nothing about the Mississippi case but had investigated other deaths by hanging or strangulation.
article_snippet: Martin said these are general observations and that "the facts are what make or break the Mississippi case.
article_snippet: Mississippi chapter President Derrick Johnson issued a statement calling on "federal authorities to immediately investigate the hanging death of Mr. Otis Byrd.
article_snippet: The FBI already is looking into any federal civil rights violations and has a forensics team on the scene.
article_snippet: The U.S. Department of Justice Civil Rights Division and U.S. Attorney for the Southern District of Mississippi are also investigating, according to a spokeswoman for The U.S. Department of Justice Civil Rights Division.
article_snippet: The Mississippi Bureau of Investigation also is investigating.
article_snippet: CNN's Ed Lavandera and Jason Morris reported from Mississippi, and CNN's Greg Botelho wrote this story from Atlanta.
article_snippet: CNN's Evan Perez, Alexandra Jaffe and Wesley Bruer contributed to this report.