South Carolina authorities continue to gather evidence from a party attended by in November at which he was photographed allegedly smoking marijuana, but even as more arrests are made and witnesses interviewed, what's still unclear is what might happen to the 23-year-old Olympic swimmer.
A lawyer representing a man who attended the party said the Richland County Sheriff's Department investigation seems to be targeting Phelps - to the point investigators are asking questions only about the 14-time gold-medal winner.
But Phelps, who has hired a lawyer, hasn't been charged with anything or been contacted by the sheriff's department, according to Drew Johnson, a representative from Phelps' management company, Octagon.
The Richland County Sheriff's Department has arrested eight people who attended the party near the University of South Carolina, according to Dick Harpootlian, a Columbia, S.C., defense attorney and former district attorney in Richland County. Harpootlian represents one of the men who was at the party and was a renter at the house where the party took place.
His client was arrested last weekend at another house, where police found a small amount of marijuana.
"All of the questions they asked him were related to Phelps," Harpootlian said.
That left the attorney with no doubt investigators are making arrests in an attempt to gather information about the swimmer.
"There's no question that this would not have occurred the way it did if was not involved," said Harpootlian, who oversaw many drug cases as a prosecutor. "It's silly that they've taken eight kids and arrested them like this. I don't think it's a valid use of very limited law enforcement resources."
Richland County authorities - namely Sheriff Leon Lott, who publicly vowed that Phelps would receive no special treatment because of his celebrity - have not said what charge Phelps might be facing. Under South Carolina law, possession of one ounce or less of marijuana is a misdemeanor that carries a fine of up to $200 and 30 days in jail for the first offense. Possession of drug paraphernalia is a $500 fine.
Jack Swerling, a criminal defense attorney who has practiced in Columbia for more than 30 years, said he has known Lott for 30 years and called him an "honorable" man who is in a difficult position.
"I think you have to consider that having this news in an English newspaper put Columbia, South Carolina, on the map in a way no one wanted," Swerling said. "Here's the sheriff of our county, and everybody is looking at this big pot party in Columbia. Does he do nothing and get criticized for that? Or does he do something and get criticized for that? He's kind of damned if he do and damned if he don't."
Swerling said simple possession charges are usually handled one of two ways if the defendant has no prior drug offenses.
Many cases are sent to pretrial diversion, meaning the defendant submits to drug counseling and testing for a short time. Once the requirements are completed, charges are usually dismissed and wiped from the defendant's record. In other cases, the defendant pleads guilty but a judge withholds the sentence for 90 days and orders urine tests and possibly community service. Again, the charges are usually expunged from the defendant's record once those requirements are met.
"I would be shocked if this case is handled any other way. I don't foresee any circumstance where jail is even a possibility," Swerling said. "The same rules should apply, whether we're talking about or not."
Harpootlian said he has asked investigators why they're acting the way they are.
"They say that no one is above the law," he said. "But this isn't a question of someone getting preferential treatment to his benefit. He's getting treated differently to his detriment."
Kenneth W. Gaines, a professor at the University of South Carolina law school with expertise in criminal procedure, said he sees no chance that Phelps will face anything worse than a simple possession charge but thinks the swimmer could do himself a favor by turning himself in.
"Cut them off at the pass," Gaines said. "You say, 'I'm doing this because kids look up to me and I want them to see me abiding by the law.' ... Why let all of this draw out? On the legal side, he's not going to be hurt at all."
If Phelps were charged and decided to fight it, a case against him would almost certainly have to be built using witness testimony, according to Andrew D. Levy, a Maryland criminal defense lawyer and adjunct faculty member at the University of Maryland School of Law, where he teaches criminal law.
Levy characterized the investigation as "a little silly" but tried to explain what the sheriff's motives might be.
"It could simply be an effort by a local elected official to get his name in the paper. ... But here is what I think the sheriff would say: Because is not a normal person, because he's the world's most famous athlete, it makes the consideration to prosecute by that law enforcement official different. Because he is so famous, it makes the harm that can flow from his conduct, and a failure to prosecute him for that conduct, that much greater."