<I think there may always be a small chance for failure>
There was a post from Ildran back in 2005 that listed fumbles as hindering spotting a trap. However, if this is the case, it has to be set up so you can recover from a fumble 100% of the time with the proper training.
In the last 40+ levels and thousands of boxes during them, I haven't missed spotting a single trap on the first try even though I still break a pick or fail to disarm a trap due to a fumble occasionally (I can't remember the last time I actually set off a trap due to a fumble.... prolly the next time I try to disarm one now that I've said something).
Starchitin
A severed gnomish hand crawls in on its fingertips and makes a rude gesture before quickly decaying and rotting into dust. A gust of wind quickly scatters the dust.
