I know it's guess work, but you make some very good points. The boiling phenomenon would sorta fall in line to what happens when one gets the Bends after deep diving. You're going from a heavy pressure environment to a low pressure (or nearly NO pressure) environment in an instant. Even a dead body (of someone who's just been killed) would still have oxygen/nitrogen in the blood--and it's going to react.

This brings to mind another thought. Divers sit inside pressure tanks before and after dives to avoid the Bends. If a killer wanted to hide the fact that a body would be exposed to space, might it be possible to use the airlock to depressurize the dead body *before* exposing it to the vacuum?