DETOURS ON THE TRAIL OF THE BOMBERS

On the same day that Stephen Jones announced he would be defending Timothy McVeigh in the Oklahoma City bombing case, he hired a security firm to protect his home outside Enid, Oklahoma. But that has not stopped the phone calls. Late last week the 54-year-old lawyer received a threat from someone the fbi believes is a known violent offender. "I have to take this seriously," Jones says. "The man said if I represented McVeigh, he was going to send a Ryder truck to my house and blow it up."

Jones understands that he has set himself up for many such threats. He realizes too that in the coming months it will be necessary to explain repeatedly to Americans horrified by the blast why the Timothy McVeighs of this world deserve legal counsel. But the Louisiana-born, Texas-bred, aw-shucks county lawyer tells Time that he is fully prepared to stick with his role as champion of the underdog. After all, he has supported losing causes before: Nixon and Roger Dale Stafford, Oklahoma's most notorious death-row inmate, and his own three unsuccessful bids for electoral office. Says Jones of his court-appointed mission: "I think lawyers have to give something back to the state and the profession."

That task was made more difficult last week as evidence against Jones' client mounted, suspects were tracked down and prosecutors organized their case against McVeigh and his Army buddy Terry Nichols. The latest person drawn into the FBI's dragnet is Steven Garrett Colbern, 35, who was picked up Friday on an unrelated weapons charge in Oatman, Arizona. Colbern, a biochemist, lived in Oatman, about 20 miles from Kingman, where McVeigh once resided. There are a number of coincidences involving Colbern: he owns a brown pickup truck similar to one a witness allegedly saw alongside McVeigh's car in Perry, Oklahoma, the day of the bombing; he used the same Kingman mail drop as McVeigh; and agents found a letter addressed to ''S.C.'' among McVeigh's effects. One federal investigator, however, cautioned that Colbern was being sought as a possible witness, not as a suspect. Said another source: "The connection of any of this to the bombing is nebulous at best."

Earlier in the week Nichols was charged with "malicious damage" to the Alfred P. Murrah Federal Building and with aiding and abetting McVeigh. According to an official affidavit presented last week, Nichols began stockpiling large amounts of fertilizer last September in several lockers near his home in Herington, Kansas. When agents searched Nichols' home after he turned himself in to police on April 21, they found 60-ft. primadet cords with blasting caps, fuel meters and a receipt for fertilizer that had McVeigh's fingerprints on it. During the search, Nichols allegedly asked the agents not to "mistake household items" for bomb ingredients, explaining that he was selling ammonium nitrate as plant food at gun shows. The affidavit revealed that Nichols wrote a letter to McVeigh last November, instructing him to clear out the lockers in case of Nichols' death. "Go for it!" Nichols wrote to his Army buddy.