He said there was a "culture and informal pressure of having targets and expectations" in police forces.
Another possibility for the discrepancy was that more low-level crimes were being dealt with informally and outside the formal crime recording system.
Mr Flatley also suggested it was also "possible" that reductions in police budgets and officers meant fewer offences were being recorded.
More top news
The move, which had been expected, was made on the recommendation of FBI disciplinary officials.
The voicemail left on a landline was not heard by a state DoT employee until Friday.
Officers were called to the house at 7.43pm on Friday, and a 35-year-old man was arrested on suspicion of murder two hours later.