Many reported times are unreliable due to differences in timing methods if not intentional falsifications. The fastest time officially recorded by the NFL was 4.29 seconds by Deion Sanders in 1989 [1], although the NFL did not begin electronic timing until 1990. In the electronic timing era, the fastest recorded time at the NFL Combine was 4.25 seconds by cornerback Fabian Washington in 2005. [2] Most other times close to 4.0 are untrustworthy due to the use of hand timing, but it is often claimed that players including Sanders (4.17)[3], Ted Ginn Jr. (4.06)[4], DeAngelo Hall (4.15)[5][6], Michael Vick (4.25)[7], Bo Jackson (4.12)[8], Michael Bennett (4.13)[9], Randy Moss (4.25)[10], Darrell Green (4.15[11], 4.2[12]), Laveranues Coles (4.2)[13], and Alexander Wright (4.09)[14] have approached that mark. Although 40 yards is always run, the 60 meter dash is not a well-regulated track and field distance, the official record for which is 6.39 seconds. Tapes of sprinter Ben Johnson's world-record breaking 1988 100 meter dash (which was later annulled due to Johnson's steroid use), however, show that Johnson ran the 60 m in 6.37 seconds; this is considered the most quickly started race ever run.[15] Johnson covered the first 40 meters in 4.53 seconds. It is often reported wrongly that Johnsons first 40 yards was timed. It was actually his first 40 meters. Which translates to an exceptionally fast 40 yard time (4.24 seconds).
However, in track and field races, the runner must react to the starting gun, which can take 0.10 to 0.20 seconds. For electronically timed 40 yard dashes, the runner is allowed to start when he wishes, and a timer hand-starts the clock (after a reaction time of 0.1 to 0.2 seconds). This difference would indicate that, at peak form, Johnson would have been electronically timed in 4.04 to 4.14 seconds, or hand-timed in about 4.00 seconds, making claims of hand-held times in the 4.1-4.2 range more credible.