Edit to add: i'm just talking about the rash of strychnine poisonings related to LSD usage in the early 2000s. it put a real damper on the party for a long time and for a lot of people.
It never happened. I've heard varying versions of this urban legend from the late eighties through to modern time. The reality is that an LSD trip can cause physical discomfort, especially toward the end. Sometimes this discomfort is stronger than other times. For some reason, people have confused this with strychnine.
There is no avenue in synthesis or purification in which LSD and strychnine would come into contact. There is no benefit to cut LSD with strychnine. The amount of strychnine necessary to have any effects on humans is too close to the lower end of lethality to be a useful cutting agent.
That being said, there are side-products in LSD synthesis or purification from natural substances (e.g. ergot fungus cultures) can leave related substances as impurities. These can cause vasoconstriction, which is unpleasant. This isn't strychnine, and it's unlikely to be dangerous as small amounts of impurity. It doesn't feel very nice, and it can cause bruising. Or, people tripping can just bump into things and be clumsy. Either way, the explanation that this comes from strychnine is and has always been bunk.
It should be obvious, but please don't confuse any of this with an endorsement of the drug. That's a separate topic. The most I'll say here is that I don't recommend it.
In some local areas where these urban legends were retold, that may be the case. My understanding is that the main reason why LSD usage faded was because the supply went down. There are plenty of factors here: reduced access to precursors, different classifications of certain pharmaceutical precursors, different farming techniques that prevent other "natural" resources, retirement and arrest of major suppliers, and a shift in taste toward other drugs that reduced demand and fouled the risk / reward calculus for doing a synthesis run.
Here in Florida, back in the eighties and nineties, an old timer with a background in organic chemistry used to make it. He was a fascinating fellow. He didn't make it for the money, and allegedly if you were introduced to the guy, he'd practically give it away. By the mid-2000s, he was no longer gifting folks his "samples" or even talking about his hobby. I'm sure he has long since passed on.
Edit to add: i'm just talking about the rash of strychnine poisonings related to LSD usage in the early 2000s. it put a real damper on the party for a long time and for a lot of people.