2 important questions inspired by a dream i had last night.

in my dream i was being accused of murder and i was pretty sure i hadn't done it but i didn't have an alibi. i told them "i was on dis at the time, look you can check." the reason i had become a suspect was that whilst at a funeral i had started uncontrollably giggling and this lead the police to believe that i had done it.

so, my two questions are:

1) would being on dis be an appropriate alibi in court? would it count?
2) what is the correct etiquette should one suddenly burst into giggles whilst at a funeral? run away? plead hysteria?