State of Oregon vs. Daniel Joseph Kammer
Mr. Kammer had been stopped for driving drunk, and was found to have a butterfly knife concealed in his pants pocket. Therefore he was charged both with driving under the influence of intoxicants and with carrying an illegal concealed weapon.
In Oregon there are no laws banning the possession, manufacture, or sale of any type of knife. However, it is a Class B Misdemeanor to carry "concealed upon the person any knife having a blade that projects or swings into position by force of a spring or by centrifugal force and commonly known as a switchblade knife, any dirk, dagger, ice pick, slung shot, metal knuckles, or any similar instrument by the use of which injury could be inflicted ..."
Mr. Kammer's court-appointed attorney retained me to testify as to my opinion of whether or not this butterfly knife was a switchblade knife. My expert opinion was (and is) that it is not. I stated that a butterfly knife requires considerable manipulation, in addition to centrifugal force, to be opened fully. I also stated that a common pocketknife is more similar to a switchblade knife than a butterfly knife is.