Prisoners held in the sixth-floor Witness Security unit of the Metropolitan Correction Center, from which convicted murderer Bernard C. Welch and fellow convict Hugh T. Colomb made a daring escape May 14, routinely received uninspected packages, according to court testimony here.

Gene Newby, 26, who was housed on the sixth floor at the MCC at the time of the escape, pleaded guilty in U.S. District Court today to contributing two drill bits and two hacksaw blades to the effort. Newby and his lawyer maintained that when fellow prisoner Larry Vaughn, 33, asked Newby to arrange for the tools to be sent in, he did not know who they were for. Vaughn was convicted June 15 of "aiding and abetting" the escape.

Welch, 45, was serving 144 years to life for burglary and the 1980 murder of Washington cardiologist Michael Halberstam. Colomb, 31, was serving 48 years on a variety of charges, including voluntary manslaughter.

U.S. District Court Judge Susan Getzendanner, describing the policy that allows some inmates at the 26-story, mixed-use jail to receive uninspected packages as "incomprehensible," today added nine months to Newby's 25-year term on a second-degree-murder conviction.

The hacksaw blades were sent to Newby at the jail in the soles of a pair of gym shoes; the two drill bits were hidden inside a pump dispenser for toothpaste.

Newby was serving a sentence in Arizona for the murder of his stepfather when an undisclosed role in the Witness Security program got him a transfer to the MCC, according to an assistant U.S. attorney here.

Newby, a slight figure in navy prison overalls, barely spoke during his 45-minute court appearance today. His court-appointed lawyer requested a concurrent sentence, but Getzendanner refused.

Also appearing in federal court this morning was Vaughn's cousin by marriage, Harvellen Vaughn, 40, of Chicago, charged with smuggling marijuana into the sixth-floor MCC unit. Prosecutor Ira Raphaelson said Harvellen Vaughn "did a favor for a bad man . . . but she has been cooperative, and it was a single incident in an otherwise law-abiding life." Judge Nicholas Bua gave Vaughn a year's probation.