Does a beam weapon have to hit a crew member - or just the square they're in?

The Anti-Bio beam in FTL only damages crew, and - as with any beam weapon - it's often tricky to line up the perfect shot on an enemy ship. I understand (based on answers to this question - How do beam weapons damage enemy crew?) that a beam's path must specifically cross crewmembers - and not just the room they're in - in order to deal them damage.

Is it sufficient, however, for the beam to hit the square / tile containing the crewmember - or does the beam's path literally have to cross through the actual crewmember's sprite? That is, if a beam 'cuts the corner' of a square containing a stationary crew member, but doesn't actually touch the crew member, will they still take damage from the shot?

I have had a beam hit an enemy crewmember when I had simply drawn it through the center of the room he was in, and believed that it would miss him. (I was quite lucky it did, since that got me the "kill three enemies with one beam" achievement.) If the crewmwmber's hit box is any smaller than the square he's occupying, then it could only be by a pixel or so. Either way, the beam does not need to cross the crewmember's sprite - passing through his square (or his hitbox, which is nearly indistinguishable from his square) is sufficient.