[chief lee runamok]

It has a nob on the blade on it to assist with opening - you can use your thumb to
flick it open with ease, in a blink.

That's so. That is why I mentioned to be accustomed with the opening of the blade
there had to be some familiarization or practice with the tool.

In this case it was possession of the knife with "malice aforethought".

[Mr Rogers]

Thousands of knives open with a thumbstud. That or a flipper open most locking knives. It takes about 10 seconds to become okay at opening. In this case, either he carried the knife already open in his bag or he opened it while concealing it inside his bag. The former would suggest he was looking to kill somebody that day. The latter is something anyone can learn to do in a minute.