David didn't bring a new victim over to Dean's on the night of the party. He was never present at Dean's on August 7th or 8th, 1973.
There was no victim, living or dead, in Dean's basement the night of the party. Dean and Wayne's last victim died on August 1, 1973 and had already been buried in the boat shed by the time the party takes place. Ergo, the trip to bury the two corpses never took place.
By all accounts, the wine that was drunk at the party wasn't laced with drugs. Wayne and Tim had drunk alcohol, smoked pot, and "huffed" paint fumes earlier that evening at Dean's. They left Dean's around midnight and returned around 3:00 AM with Rhonda. The three of them drank alcohol and Wayne and Tim huffed more paint fumes as well.
The film indicates twice that Dean paid Wayne and David $1500. for each victim they produced. This bit of mis-information actually came from Henley himself. As he sat in a police car talking to reporters, he was asked how much he was paid. Henley answers "He said $1500." He never said he was paid that much; just that it was offered. The pair were actually paid $200. per victim. The correct quote "If you weren't my friend, I could have gotten two hundred dollars for you" was said by Wayne to Tim, as they waited with Rhonda, for the police to arrive at Dean's on August 8th.
In last moments of the film, we read "With the assistance of Wayne, Police we able to locate the remains of 27 teenagers and children from underneath Dean's boatshed." While it is true that the total body count at the time was 27, most investigators believe that there are "at least 28 victims" of Wayne and Dean. All the victims were teenagers and none were younger than 13. Only 17 bodies were recovered from the boat shed, though Wayne insisted that there were 2 more. The other 10 bodies were found on a beach, at a lake, and by a roadside.
When Rhonda's dad is chasing after Wayne's car, he passes by a 1988 Oldsmobile. The film takes place in August, 1973.
Among Dean's many cat figurines is a giant Garfield figurine. The first Garfield comic strip was published in June 1978, but the film takes place in August, 1973.
The soundtrack to the film Caligula is seen in Dean's record collection. Caligula came out in 1979, but this film takes place in August, 1973.
One character says the phrase "stressed out". That phrase was unknown in 1973. Merriam-Webster tells us that the earliest known occurrence of "stressed out" was in 1983.
All of the songs on the soundtrack, except for three, were not in existence at the time the film takes place. The film takes place on the night of August 7 and morning of August 8, 1973. Only the songs "Love or Let Me Be Lonely" (Friends of Distinction, 1970), "Backstabbers" (O'Jays, 1972), and "Love Train" (O'Jays, 1972) could have been heard at that time.
Wayne grabs the empty bottle of wine and promises to refill it for Rhonda and Tim, so that he can put the sedatives in their drinks. Instead, he puts the sedatives in the empty bottle and gives it back to them.