No "booby traps". As tempting as it may be to zap a potential thief, imagine being booked when little Johnny, the 5-year old neighbor kid, decided to put a hand on the pretty bicycle...

The law has consistently held against any sort of theft or burglary-preventing traps, and even awarded money to the thief for any injuries incurred.

In some states, you are able to use force (even deadly force) to prevent property crimes. In most, this is not the case. You may legally attempt to take the person into custody if you witness him trying to commit a crime, but this is filled with peril.

Far better to rig up some sort of surveillance video system. Likely the thief is known to local police, and they can take care of any prosecution.