An examination of the entries within billet pass-book on 15 February indicated Cummins had reported back to the billet before 10:30 p.m. on several dates each murder and attempted murder investigators had ascribed to the Blackout Killer. However, many entries had been written in lead pencil, meaning entries within the book could easily be manipulated. Furthermore, several of Cummins's entries for the month of February were incomplete, as although he had invariably signed the pass-book when leaving base, he had frequently failed to sign in upon his return. Questioning of Cummins's fellow airmen revealed they had been in the habit of vouching for each other's return to base, and that Cummins had spent extravagantly in the week prior to his arrest. Detective Chief Inspector Edward Greeno further discovered Cummins and another airman named Felix Sampson had left the billet via a fire escape after midnight on each of the dates in question, and both had not returned to base until the early hours of the morning.