Personally I think it didn't exist and it was abrasions or something of that sort and it is just Smit trying to prove an intruder did it. A theory is that Mr .Smit had just closed a case where everyone though the parent or someone committed a crime and he was the only one who thought differently. It turned out he proved everyone wrong. So could this simply have just been him trying to be hero again. That i'm not so sure of, in any case do you think a stun gun was used or not?