Methanol gets into them because it’s a product of the fermentation. As the yeast breaks the sugars down, some is made into ethanol and some into methanol. I dunno how a legit distillery does it nowadays but historically, since methanol has a lower boiling point, you’d throw away the first bit of distilled liquid that you get and hope you judged correctly when all the methanol was distilled out.
The fermentation process creates all kinds of stuff besides just the ethanol we know and love. When distilled, the first stuff to come off the still (foreshots and heads) are gross-tasting and potentially dangerous things like methanol and acetone. You then get into the hearts, the good-tasting ethanol component of the distillation process and eventually the tails, poor tasting but not dangerous heavier volatiles that show up at the end.
The problem is in quality control, or lack thereof. A less discriminating producer of booze won’t throw out the bad stuff, seeking quantity over quality. Additionally, back in Prohibition, really unethical producers would cut the booze with other terrible junk to cover up unpleasant flavor or simply sell more product with cheaper ingredients. Of course we still see that today with street drugs being cut with all sorts of unpleasant things. Who would you complain to?
The thing to keep in mind is that it’s a matter of concentration; 5 gallons of beer has the same amount of methanol that 5 gallons of undistilled whiskey wash does. The difference is that in beer, it’s distributed in 5 gallons, but in whiskey, that same amount of methanol would be distributed in maybe a gallon worth of distilled whiskey.
So distillers don’t include the foreshots or heads, thereby reducing the overall amount of methanol in the finished product. (foreshots are pretty much straight poisonous, while heads are essentially tainted whiskey, so they’ll often redistill those later)
It’s also why freeze-distillation/concentration as used for beverages like traditional applejack has a reputation for titanic hangovers, as the process concentrates everything- methanol, ethanol, etc… by removing water.
It is my understanding that typically when you hear about methanol poisoning from moonshine or whatnot, it’s not so much poor distillation processes as much as purposefully cutting the distillate with methanol (which is cheaper.) If you’re sloppy and leave too much of the heads in, the worst that happens is that you get a wicked hangover.
Rarely is methanol added to spirits if they are being adultered since as mentioned its a by product of fermentation so the easiest way to get it already is giving you booze. People do make terrible heads cuts or have failures on stills that do the cuts for you. Freeze distillation also just brings along the heads while cutting the tails and water.
While methanol does appear in most fermentations it chemically comes from the break down of pectin and so fruit spirits are more likely to have it than grain spirits it also is more present when wood like stems are included in the distillation which is why methanol is sometimes called wood alcohol.
The most common thing to cut spirits with is glycol or glycerin since it adds to the body of the spirit. In small doses it’s ok but in large doses it’s deadly.
There is some methanol (and a bunch of other alcohols) made during fermentation, particularly if the yeast is stressed, but if there’s enough to seriously poison the drinker it’s because someone has added meths or tried to distill it to get the ethanol out.
The methanol isn’t evenly distributed in how it comes out of a still. That creates the potential for all the methanol in a large batch to be concentrated together. If they keep the heads and don’t mix the output of a large batch together there’s going to be a couple containers that are methanol heavy while the rest are relatively methanol free.
The only time I’ve ever heard of that was when a relative of mine mentioned that she was at a party where someone spiked the drinks with rubbing alcohol. A handful of people woke up the next blind, one person went to another party and had ‘regular’ alcohol (ethanol) which, as it turns out, is an antidote.
As for how it gets into liquor. I couldn’t tell you if making your own spirits incorrectly can result in that, but it wouldn’t surprise me if people, not knowing there’s a difference, spike homemade (or store bought) booze with rubbing alcohol.
Sure, Everclear would be safer, but if you don’t know how dangerous rubbing alcohol is, it’s a whole lot cheaper.
“Rubbing alcohol” is isopropyl alcohol, not methanol. It’s not good for you, but it’s not as toxic as methanol. Isopropyl is metabolized to acetone, not formaldehyde and formic acid. It doesn’t cause blindness or the sort of acute nerve damage that methanol does.
So I have to wonder if the tale you relate didn’t get garbled on the way to your ear.
But I could see people being stupid enough to spike the punch with all sorts of random alcohols/other stuff, especially when already drunk or high.