Roger Nicholson was nine years old in 1982 when Tylenol capsules laced with cyanide began turning up in Chicago-area pharmacies. He can still remember his panicked mother throwing out the family supply of pills following the deaths of seven people, a crime that prompted widespread hysteria and forever changed the way medication is packaged.

Yesterday, Mr. Nicholson found himself walking down his Cambridge, Mass., street with neighbour James Lewis, the man long suspected of being responsible for the crime.

Mr. Lewis and his wife, Leann, were ordered this week to submit fingerprints and DNA samples to law-enforcement officials, the first major development in a decades-long investigation centred on the pair.

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Mr. Nicholson struck up a relationship with Mr. Lewis after learning that the alleged Tylenol Killer lived on his street, and said yesterday that the 63-year-old had complied with the court order.

"He doesn't think they have anything," he said.

The unexpected development in the case is the latest chapter in a bizarre crime saga that began with the death of 12-year-old Mary Kellerman.

On Sept. 29, 1982, the Illinois girl told her parents she didn't feel well and was given an extra-strength Tylenol. When she collapsed on the bathroom floor, doctors believed at first that she had died of a stroke.

But the same day, a 27-year-old postal worker named Adam Janus was rushed to the hospital, dead from what looked like a massive heart attack.

That night, Adam's younger brother, Stanley, and Stanley's 19-year-old wife, Theresa, gathered at his house to mourn. Both reportedly had headaches brought about by grief and stress, and Stanley found a bottle of Tylenol on the kitchen counter. The couple took the pills and collapsed. Stanley died that night, his wife two days later.

Three more people, including a new mother battling post-labour pains, died before authorities linked the deaths to Tylenol, prompting a recall of 31 million bottles of pills and the introduction of tamperproof bottles.

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Mr. Lewis was arrested in December of 1982 at the New York Public Library in Manhattan after sending an extortion letter to Johnson & Johnson, the manufacturers of Tylenol, demanding $1-million to stop the killings.

"If you don't mind the publicity of these little capsules, then do nothing," he wrote. "So far, I have spent less than fifty dollars. And it takes me less than 10 minutes per bottle."

He was convicted of extortion, but claimed he was trying to frame someone at the bank where he asked the money to be sent. He denied responsibility for the murders.

He served 13 years of a 20-year sentence and was released in 1995, but investigators have long said he remains the prime suspect in the case. Mr. Lewis and his wife were staying in a hotel in New York when the murders occurred, and investigators have been unable to find evidence connecting either to the crime.

Chicago resident Roger Arnold was also investigated and cleared of the killings. He blamed the owner of a local bar, Marty Sinclair, for fingering him to police. In 1983, he argued with Mr. Sinclair in his bar and returned with a gun, but shot and killed John Stanisha by mistake. He was convicted of second-degree murder and served 15 years in prison.

Mr. Lewis has had other brushes with the law, before and after his extortion conviction.

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In 2004, he was arrested for allegedly kidnapping and raping a Massachusetts woman, but the charges were dropped after the victim refused to testify.

In 1978, he was charged in Kansas City with killing his boss, 73-year-old Raymond West. The charges were dismissed because of a problem with the legality of some of the evidence.

He allegedly also sent a letter to president Ronald Reagan, threatening to kill him using a remote-controlled plane.

Mr. Lewis moved to Cambridge, a suburb of Boston, after his release from prison in 1995. Mr. Nicholson first encountered him when leaving a local store, and immediately recognized him as the man connected to the Tylenol murders.

The host of a local cable-access talk show called The Cambridge Rag, Mr. Nicholson invited Mr. Lewis to be interviewed after ambushing him in the neighbourhood.

Since then, the two have kept in touch, and Mr. Lewis called Mr. Nicholson yesterday hoping to appear on The Cambridge Rag tomorrow to promote his self-published book, a thriller called Poison: The Doctor's Dilemma, released as an e-book on Jan. 1.

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"A rogue government employee, Agua Naranja, triggers earthquakes, threatening to level a Midwestern city. Meanwhile, underground water supplies have been poisoned and people are dying. Terror, hysteria and eternal vigilance breed mistrust of public authority," reads the description on Amazon.com.

Federal agents searched Mr. Lewis's home last February, and have said new technology could lead to a breakthrough in the investigation. But Mr. Nicholson remains doubtful that his acquaintance will ever be prosecuted for the Tylenol killings.

"I wish I could say, 'Yeah,' " he said. "I just want to know if he did it."