The wiki piece you are quoting from doesn't support your conclusion. Extenuating cicumstances when taken into consideration mean that instead of the jury meting out punishment the Judge does. The jury still reach a verdict of guilty or not guilty based on the evidence. Your "less at fault" scenario is a figment of your imagination .
Extenuating circumstances means exactly what I posted--that the punishment is reduced. Reduced punishment effectively means less fault. These are facts.