Part 9
Initial investigations were conducted by Sheriff W. H. Doran and the County Attorney J. Mitch Johnson, which yielded no immediate clues or arrests. The grand jury convened in October 1933, spent days hearing testimony, but returned no indictments, fueling speculation that the case was either an accident or covered up due to influential individuals involved. Rumors and theories abounded: some believed Robertson had been beaten and left to die, while others clung to the accident narrative of a fall from the window. The proximity of an all-night café just 100 feet away and people on the streets made it baffling — how a body could be dumped without witnesses, suggesting the murder—if it was one—occurred elsewhere and was staged to look accidental. 40
The case lay dormant until the spring of 1934, when the Texas Rangers were assigned to reinvestigate. Ranger Sergeant Joe Osoba, a seasoned lawman with a background in local policing, led the effort alongside Ranger Hume C. Graves. Osoba, born in 1885 and with multiple enlistments in the Rangers during the 1920s and 1930s, was known for his work on bootlegging and bank robbery cases. Graves, enlisted in 1933 at age forty-four, brought experience from bank examining and highway corruption investigations. This was at a time when the Ranger force was moving from their old Frontier Battalion roots into modern law enforcement. 41
By May 1934, the Rangers' probe led to dramatic arrests. Deputy Sheriff Nathaniel H. Sellman, who had been appointed under Sheriff Doran in 1932, was charged with murder and held in an undisclosed jail. Eight others were arrested and held in separate jails in connection with Robertson's slaying, with Osoba announcing that more arrests were expected. Sellman, released from duties just prior, faced a murder complaint filed by Sheriff Doran after Ranger notification. District Attorney F. H. Hammond prepared for a special grand jury session, highlighting the intensity of the investigation that revealed Robertson was killed elsewhere and his body moved to the sidewalk. 42