An Alexandria teen-ager who had just been sentenced to three months in jail on a grand larceny conviction yesterday bolted from the Prince William County courthouse through a bathroom window.

His escape plan hit a snag, though, when he landed next to the county's new jail warden, Gene A. Scroggy, who was talking to an assistant prosecutor.

"I was coming back from the bank and stopped for a minute," said Scroggy, an unconventional warden who once posed as an ax murderer to assess conditions in his own Pennsylvania prison.

"I heard this crash behind me and turned to see this kid coming out of the window. I figured if he had to leave the court through a window then he had no business leaving the court."

Scroggy yelled for assistance from nearby city police and sheriff officers, then chased the youth down the street, behind another court building and into the arms of two policemen who were alerted by Scroggy's call.

"I'd just gone out for a 3 1/2-mile run a couple hours before so I was pretty wore out by the time I got there," said the 43-year-old jailer.

No additional charge had been brought against the juvenile by late yesterday, a court spokesman said.

After his capture, the youth was taken to the Prince William County-Manassas Adult Detention Center -- the jail presided over by Scroggy. "We've got him right here safe and tight," said Scroggy yesterday afternoon. "He just picked one bad time to go jumping out of a window."