According to http://www.drugabuse.gov/publications/drugfacts/nationwide-t... , about 0.4% of the US uses a hallucinogen each month. According to http://www.niaaa.nih.gov/alcohol-health/overview-alcohol-con... about 60% have had alcohol in the same month.
Thats a ratio of about 150. Let's round it up to 200.
Nearly 88,000 people die from alcohol related deaths per year (see http://www.niaaa.nih.gov/alcohol-health/overview-alcohol-con... ).
Thus, if the risk factors for death related to hallucinogens is higher than that of alcohol, I would expect to see about 440 such deaths per year.
10,322 died due to alcohol-impaired-driving. Using the same ratio, I would expect to see about 50 such deaths related to hallucinogens.
I have failed to find deaths of the sort you described, which make me doubt that there's a simple causal relationship between the number of fatalities and the prohibition of a substance.