They also were charged with endangering the welfare of a child, because Dassay's infant was in the home during drug sales, police said. Dassay's girlfriend also lives in the house but was not charged, police said. Dassay is wanted on drug charges by police in other states, authorities said.
Also charged were two Drexel students who bought drugs from the group and later assisted police in the investigation. Their names were not released because they acted as confidential informants.
Drexel said in a statement that it had a "zero-tolerance policy" for illegal activity.
"When Drexel is made aware of any students participating in illegal behavior, the university places them on indefinite suspension pending the outcome of the investigation," the statement said.
Authorities say they believe the ring had operated near campus for more than a year, District Attorney Seth Williams said.
The investigation began Jan. 18, after police in Upper Moreland Township contacted Philadelphia authorities upon arresting a Drexel student on marijuana and gun charges. The student told police he had information about an acid ring, then allowed the District Attorney's Office to record phone calls between himself and another student arranging a drug transaction.
After the second student was arrested, he also agreed to cooperate, police said.
Police say they think Dassay, Crawford, and Zappala used a multistep process in which buyers had to meet with Crawford or Zappala on the street, hand over money, and wait until they returned with the drugs.
The case prompted local officials to brush up on their knowledge of LSD, the mood-altering substance that is rarely the center of a large-scale drug operation.
"Frankly, nobody had dealt with an acid ring in this area for upwards of about 15 years," said Brian Grady of the Dangerous Drug Offender unit of the District Attorney's Office.
LSD is made from a fungus that grows on rye. It is ingested with blotter paper or in liquid form and can cause strong hallucinations, delusions, or altered thinking, including a distorted sense of time and space. It is considered nonaddictive but can have long-term effects such as "flashbacks," in which the user experiences sensations after the drug has worn off.
Contact staff writer Allison Steele at 215-854-2641 or firstname.lastname@example.org.