"He was very artistic," Barbara MacKay-Bush said this week. "That's why I think he did drywalling, because to get it perfect was artistic to him."

Oddly, it's a piece of art - graffiti featuring a simple, ominous smiley face - that has MacKay-Bush and police speculating about Booth's drowning in January in a creek behind Bootlegger's Bar in Ridley Township.

Found near where Booth is believed to have entered the shallow creek, the smiley face has raised concern that his death may have been the work of a network of serial killers that two former New York City detectives believe is responsible for at least 40 similar deaths spanning more than a decade.

Last week at a New York City news conference and on "Good Morning America," retired officers Sgt. Kevin Gannon and Det. Anthony Duarte discussed their theory that a group of killers target and drown white, college-age men.

In at least a dozen of the 40 deaths in 11 states they're investigating, the retired officers said that graffiti including a smiley face was found near where the victim is believed to have entered the water.

Detective Sgt. Scott Willoughby of Ridley Township police, one of the lead investigators on Booth's case, was watching "Good Morning America" as part of his daily ritual last week when he caught the segment.

"I was shocked at all the similarities I had," he said.

At the township police station, Willoughby rattled off the likenesses between Booth's case and the 40 cases in the Midwest and Northeast that the detectives have identified: Booth was a white male between 18 and 25, between 5 feet 8 and 6 feet, and between 150 and 200 pounds. He drowned after a night of drinking at a college bar and he had no visible signs of trauma. When his body was found, he had his money, ID card and wallet but not his cell phone.

And there was the smiley face - replete with a crown - painted below the back deck of Bootlegger's, where Booth is believed to have entered the creek.

Timothy Kephart, a Gloucester County native who is the founder and president of Graffiti Tracker Inc., a graffiti-analysis company in Long Beach, Calif., said that he was familiar with the retired detectives' smiley-face theory.

"I don't necessarily know if there's a smiley-face killer out there," he said. "I'm not saying these guys are dead wrong, but the commonality of graffiti being in various tagging locations is not unusual."

MacKay-Bush didn't see the "Good Morning America" segment featuring the detectives, but several members of her family alerted her to it and she called Ridley police.

"They were already on it," she said. "They said they went back to the scene and found a smiley face. Oh God, I just got the chills.

"My feeling was just that, you know, it was something that maybe would make sense," she said. "There were so many scenarios, but there was no scenario that would explain why he ended up in the creek."

Booth, of Wilmington, had gone out for a night of drinking with eight friends on Jan. 20. He'd never been to Bootlegger's Bar, on MacDade Boulevard near Virginia Avenue, a well-known hangout for Widener University students.

Throughout the night, Booth's friends either left the bar or were kicked out, Willoughby said. One friend told the others he'd give Booth a ride home, but when he went to look for him, Booth couldn't be found.

The last people to have seen Booth are a barmaid and three girls, all of whom police have interviewed.

His body was found two weeks later behind the bar, in a creek no more than two feet deep. The creek froze over and searchers were unable to find him until the next thaw, Willoughby said.

A videotape at the bar shows Booth entering, but there are two other doors to exit the bar, one of which is monitored by video. Booth could have left through the unmonitored front door or he could have left through a back door, Willoughby said.

"If he exited the front door, he would have had to walk 300 to 400 yards to get to the creek," he said. "Then he would have had to walk 25 yards to walk down the creek. From the back door, the creek is less than 30 yards."

But, Willoughby said, the creek is shielded by 15 to 20 yards of debris. It's a place where landscapers dump their logs, sticks and branches, he said.

"You would have to fight your way to get back to the creek," Willoughby said. "It's always puzzled me how he got in the water and how he drowned in a foot-and-a-half of water, but I'm even more puzzled by how he got to the creek in the first place."

Police said that Booth had a blood-alcohol level of .20 and a small amount of Xanax in his system, a level consistent with a medical prescription.

The Delaware County Medical Examiner's Office said that a report on Booth's cause and manner of death is pending toxicology results, but MacKay-Bush said that the medical examiner told her that he'd ruled it an "accidental drowning."

"After all the interviews with everyone in the bar, the general consensus was that he wasn't super-intoxicated," Willoughby said. "That gets my suspicions heightened. I don't have him falling over drunk. He's being cordial, and his friends said he was no different than he ever was."

MacKay-Bush said that it would be highly unusual for her son to go toward a body of water on his own.

"Something didn't seem right to me because he never liked the water, and there was no reason for him to be near water in the middle of January," she said.

Several police departments across the country and the FBI have already discounted the retired detectives' smiley-face theory in other cases. In a statement, the FBI said that a "majority of these instances appear to be alcohol-related drownings."

"We determined there is no serial killer or killers," Special Agent Richard J. Kolko told the Daily News this week.

Still, Willoughby has arranged for one of the retired investigators, Gannon, to come to Ridley Township later this month to determine if the case could be linked to the ones he is investigating.

"I haven't accepted the theory, but I find the circumstances puzzling, even without this theory," Willoughby said. "Some of the clues to their puzzle match some of the clues to this puzzle. That's why I think we need to investigate all clues and all avenues.

"My goal is to come up with an answer for this mother who lost her son," Willoughby said. "Whether it's obtainable or not, I don't know."

Staff writer William Bender contributed to this report.