J'maal Alexander was 18 years old at the time of the London Olympics, and was making his Olympic debut. On 4 August, he took part in the preliminary round of the men's 100 meters. Assigned to heat three, he ran his race in a time of 10.92 seconds, fourth in his heat, but only the top two from each heat plus the next two fastest overall from all four heats could advance and he was eliminated, the slowest qualifying time being 10.80 seconds. The gold medal was eventually won by Usain Bolt of Jamaica in 9.63 seconds (an Olympic record time); silver was won by Yohan Blake also of Jamaica, and bronze was taken by the American Justin Gatlin.