Sorry but I think common sense just goes a long way and I get uptight ( my problem) when people don't think things out.
Ever cut yourself and suck off or lick off your own blood. What would be best as to get some of your own blood into your own blood if not contaminated (hence inside the syringe and or needle)
Just some thinking goes a long way. Some don't agree with me about aspirating and not. But since all my years I've never seen it done IM in a hospital or Doc. Once you penetrate the shin the needle has broken capillaries and the bleed, some more then others. I would bet that more times, or most times when aspirating the blood you might see is from a capillary and not a vein. Look at some diagrams there are millions and millions. Some brining blood to the tissue and some taking blood to the heart. So don't you think some you cut get the compound in and sucked and pumped toward the heart. OF course.
So I will apologize for being harsh. But please think these things out a little more so even some of what you hear you just don't except it just because someone said it. There's nothing like sound thinking and process of elimination by your own mind and the verified by more minds. I'll try to be more cool

...crazy mike