RJ: you are absolutely correct. Any attempts to hide the knife will be seen as a furtive gesture, and will surely get you pulled out and frisked. At this point any officer, especially one alone on a dark street in a high crime area, can easily justify the frisk as long as the stop is legal. This does not require a warrant. It is just an officer safety issue.
Personally, If I find a knife during a frisk, I hold it untill the encounter is finished. I then return it unless the knife is illegal in MA., being double edged or automatic, for example. I do prefer to remove it from the person's pocket myself, rather than take any chances. I may find issue with a guy walking around with a 20" machete , but your average folder will not raise too many questions. It is best to be up front about it, and tell the officer you are carrying a knife if he askes you to submit to a pat-frisk.
As to the cleanliness of the knife being an issue, I use my Sebenza often, and always make sure it's clean afterwards, as I imagine most people would. I think cleanliness is a non-issue.
Many police officers do carry knives on duty, I carry an Emerson CQC-7 in a pouch on my belt, and an Emerson commander clipped inside my right pants pocket while on duty.
Joe
[This message has been edited by Joe Cop (edited 05-01-2000).]
[This message has been edited by Joe Cop (edited 05-01-2000).]