To be caught red-handed: Origin and meaning

To be caught red-handed means that you have been caught in the act of doing something illegal. No excuses or alibi’s can be used, as your transgression is obvious, visible and undeniable. Usually related to stealing, with the stolen goods in your possesion. Caught on CCTV robbing a store with your face clearly visible would be a good example.
To be caught in this way has a legal term “in flagrante delicto”, which loosely translated means “in the progressing misdeed”. Therefore you are caught while you are doing something you should not be doing.
The most common origin for the term red-handed is Scottish, (circa 1400ad), specifically related to poaching. In order to punish a poacher the legal system had to have undeniable proof the accused was guilty. After killing and skinning an animal, the poacher would have blood on his hands, and this would be the necessary proof required. Poacher was caught red hand, i.e. with blood on his hands.
This expression has evolved to re-handed.
Can one be caught red-handed if you are doing something legal?
If you are supposed to do something, for example, clean the garage, and you disappear to have a couple of beers somewhere in solitude. If the lady in your life comes looking for you and “catches” you loafing, have you been caught red-handed? The way I look at it, this is not possible, as all the definitions I can find refer to illegal activities.
Loafing is not an illegal activity; it could be considered a national pastime in some places I know of.