Maryland's highest court ruled yesterday that a man accused of seeking sex with a teen-ager through the Internet cannot be tried because a judge dismissed the case during pretrial arguments, but the court stopped short of addressing questions that could end police stings used to apprehend suspects on similar charges.

In a 4-3 opinion, the Court of Appeals ruled against prosecutors who want to revive charges against Donald Taylor Jr. of Camden, N.J., who was accused of traveling to Frederick in 1999 to have sex with a fictitious 15-year-old girl he thought he had met through the Internet.

Taylor, then 44, had unwittingly made arrangements with a state trooper, authorities said, and he was charged under a Maryland law that provides for a maximum penalty of 10 years in prison and a $25,000 fine for using a computer to solicit a sexual encounter with a minor.

Frederick County Circuit Judge Mary Ann Stepler, responding to an argument which has been raised in at least one subsequent case, agreed with the defense that no crime was committed because the 15-year-old girl does not exist. The judge dismissed the case.

In the ruling yesterday, the Court of Appeals did not directly address whether a crime could be committed with a fictitious underage victim. Rather, it focused on whether the judge's ruling -- however debatable its basis might be -- precluded Taylor from being tried under provisions guarding against double jeopardy.

But the dissenting opinion by three judges warned, "The majority opinion is a wake up call for trial court judges" that "takes a potentially dangerous step in the area of criminal law." The dissent warned that the decision might effectively require prosecutors to present evidence at pretrial as well as at trial because they would have no recourse of appeal if they did not present enough evidence at pretrial.

Because the opinion pointedly steered clear of the constitutional issues involving a fictitious victim, a prosecutor in Carroll County said authorities will continue using the sting tactics. More than a dozen similar cases have been prosecuted in Carroll this year.

"As far as I'm concerned, this isn't going to stop the way we investigate and proceed with these cases," said Tracy A. Gilmore, deputy state's attorney in Carroll.

In September in Carroll Circuit Court, a defense lawyer raised the issue of the fictitious victim in asking that similar charges be dismissed. No decision has been issued on that motion. Pretrial hearings in two similar cases in Carroll were postponed this month to await the appellate court ruling.

The Maryland Internet Crimes Against Children Task Force, which includes state troopers and sheriff's deputies from Carroll and other counties, has made about 40 arrests, and several defendants have pleaded guilty. In the cases, a police officer typically poses in an Internet chat room as a young girl and fields solicitations for sex. The officer then arranges to meet the man soliciting sex, and the encounter ends in arrest.

In yesterday's opinion, the high court said the trial judge in the Frederick case erred by granting defense motions to dismiss the charges because she went beyond the charging documents.

In another case that was considered together with the Frederick case, the appeals court ruled that a Prince George's County District Court judge wrongly dismissed charges of conspiring to have women "engage in public nudity."

Nevertheless, the dismissals amounted to a judgment of innocence -- and under Maryland common-law, a defendant cannot be tried again for the same offense, the court found.