Right went to play with it just now, is it at all possible that the timing could be out? would this cause this?

when i put the 1.8 sierra pulley on i put it in gear to tighten the pulley up, i know the crank isnt locked untill the gears lock up, so the engine turns abit before it locks, could at this point the belt mayb jumped a tooth? i also found the belt cracked so its about to go at anythime