I said in my post that it wouldn't be prosecutable, nor should it, as there are babies out there that sometimes have to sleep on their stomachs because of medical issues. It's still not a good idea. Many theorists think that SIDS occurs when the baby falls into too deep a sleep, so when people put them on their bellies to sleep better, they're actually helping that deep sleep along. A good compromise is to use a positioner to put them on their side.
It's good you breastfed, because that can counteract some of the effects of cigarette smoke on the baby. It is a risk factor for SIDS, but breastfeeding is a good mitigator for SIDS.
I'm not judging, but you asked. People take actions that increase the incidence of SIDS, so in that way, yes, they contribute. I, too, let my babies breastfeed in bed with me early on when it was hard to get sleep otherwise. If I had trapped them, or rolled over on them, and they died, I would have felt a lifetime of guilt. That's why I ended up buying a Snuggle Nest.
These people were drinking and snorting cocaine, and that's endangerment. If they found drugs in the babies system, I would be thrilled if it was manslaughter. I think the article title is just badly phrased. Everyone thinks that SIDS is this silent killer that comes unannounced, and a lot of times it does, but there are so many things you can do to lessen the risk. These people increased the risk and the article makes it sound like they suffocated the baby. By accident, of course, but had that baby been on its back in its crib, it'd likely still be alive. That doesn't scream SIDS to me.