Yes it does have a ball detent. That holds it closed for a VERY light shake of the wrist but anything stronger will shoot it out very fast. This happens whether the blade is facing up or down or either side. When the blade does fall it falls past the 90 degree point when facing down, resulting in a very light shake to engage. I used to like them this loose until I got reprimanded by a LEO that it was considered a gravity knife as it took virtually no strength for it to lock. When it does lock, it's a bear to get closed, definitely can't do it one-handed when the tab rides midway under the tang. Otherwise love it though.