DWF Controller did not issue mandated go-around to landing aircraft following an ASDE-X alert; noting the runway was observed clear by he and a supervisor; claiming the ASDE-X equipment had been programmed incorrectly.

Narrative

I had just assumed the Local East 3 position and inquired about the status of morning runway inspections. The Traffic Management Specialist and supervisor advised that my runway of responsibility; Runway 7L; had been inspected. At that time; I removed the Runway Incursion Device (red strip holder) indicating that Runway 7L was open. Air Carrier X had been cleared to land when this position was combined with LE-1 earlier; so I had not made any transmissions to the aircraft. Air Carrier X was on approximately a mile final when I scanned the landing runway once again and noted that the runway environment was clear and sterile for the landing. On very short final; the ASDE-X alarm activated and instructed 'Go-Around; Runway 17L'. The Supervisor stepped immediately to my position and we simultaneously scanned the runway prior to Air Carrier X crossing the runway threshold. After observing no vehicles or conflicting traffic on the runway; I remarked that 'there's nothing there' and the FLM (Front Line Manager) concurred; and I allowed Air Carrier X to land. As Air Carrier X was rolling out; I observed that the runway closure 'X's' were displayed on the ASDE-X for Runway 17L; which I quickly disabled. I was advised then that the Local Assist East Controller had forgotten to remove the 'X's' when Runway 17L was reopened after the earlier inspection. Immediately following this incident; the Local East 1 Controller loudly stated to the entire Tower Cab that ignoring an ASDE-X warning is not permissible and that all ASDE-X instructions must be complied with regardless of what is visibly perceived. While realizing this; I felt that the Supervisor's concurrence of my sterile runway environment and my double check was sufficient to allow Air Carrier X to land. While I certainly do make mistakes; one of my strengths is my runway scan and I have become accustomed to doing this when the aircraft is on approximately a mile final to any runway which I am responsible for. While I do believe that my assessment; and that of the FLM; was correct in verifying that the runway environment was safe for landing; I also accept responsibility for my error in judgment in NOT following the verbal mandate of the ASDE-X warning. In the future; it is my intention to completely adhere to and follow prescribed FAA policy; rules; and procedures as applicable to Safety Logic system alarm response expectations. This is a difficult issue for controllers of my general age and experience demographic. We often opt for common sense over indications from equipment that the FAA has spent billions of dollars creating for redundancy purposes. Perhaps the newer generation of video-game playing controllers will be more ready and willing to issue go-around instructions when they are completely unwarranted. In my case; I will also do so in the future in compliance with FAA Policy and Procedures.