Illegal Substitution/Illegal Participation

[Bpost]

A has the ball and scores. B had 12 men on the field and crew does not get it stopped so now you have illegal participation. How do you penalize? Let’s change it and say the 12th man makes the tackle before the touchdown. How do you penalize?

[ElvisLives]

You need to specify which rule set.
But, in any set, how do you know who is the 12th player?

[CalhounLJ]

A has the ball and scores. B had 12 men on the field and crew does not get it stopped so now you have illegal participation. How do you penalize? Let’s change it and say the 12th man makes the tackle before the touchdown. How do you penalize?

In NFHS the identity of the 12fth man doesn’t matter, nor does it matter if he influenced the play. If there are twelve men in the formation at the snap with none trying to leave, it’s IP fouls simultaneous with snap and if accepted is enforced 15yds from the previous spot.

[bossman72]

In NFHS the identity of the 12fth man doesn’t matter, nor does it matter if he influenced the play. If there are twelve men in the formation at the snap with none trying to leave, it’s IP fouls simultaneous with snap and if accepted is enforced 15yds from the previous spot.

Correct.  If on the TD scoring play, you can enforce on try or kickoff.

NCAA it's 5 yards previous spot.  Declined if TD.