Federal prosecutors in Manhattan are seeking a lengthy prison sentence for the creator of Silk Road, a once-thriving website that allowed users to anonymously buy and sell heroin, cocaine, LSD and other drugs online until it was shut down by the authorities in 2013.
The government, in a sentencing memo filed on Tuesday in Federal District Court, depicted the defendant, Ross W. Ulbricht, as a digital drug kingpin who ran an “online black market of unprecedented scope,” which had left addiction and fatal overdoses in its wake.
During Silk Road’s nearly three years of operation, more than 1.5 million transactions were conducted on the site, involving over 100,000 buyer accounts and nearly 4,000 vendor accounts, the government said. At the time of its closing, the site listed more than 13,000 offerings of illegal drugs.
Prosecutors have said that Mr. Ulbricht solicited the murders of people he saw as threats to his business, though there was no evidence that such killings were carried out, and that at least six deaths were attributed to drugs bought on Silk Road.
Although Mr. Ulbricht, 31, could face life imprisonment when he is sentenced on Friday by Judge Katherine B. Forrest of Federal District Court, the government, in its filing, did not ask for the maximum term.
Instead, the office of Preet Bharara, the United States attorney for the Southern District of New York, said Mr. Ulbricht should receive a sentence that is “substantially above the mandatory minimum” of 20 years that Mr. Ulbricht faces for one of the seven counts on which he was convicted.
“Ulbricht bears responsibility for the overdoses, addictions and other foreseeable repercussions of the illegal drugs sold on Silk Road,” Mr. Bharara’s office wrote. “It does not matter that he did not personally handle those drugs; neither would a traditional kingpin.”
Mr. Ulbricht was convicted in February on seven counts, including distributing narcotics on the Internet and engaging in a continuing criminal enterprise, charges that carry potential life terms.
The case has been widely watched because of its technological intrigue and because it lifted the veil on the so-called dark web, a hidden part of the Internet where transactions were conducted with the virtual currency Bitcoin and could be shielded from the ready scrutiny of law enforcement.
The government had alleged that Mr. Ulbricht ran Silk Road under the pseudonym Dread Pirate Roberts and that he took millions of dollars in commissions from deals made on the site.
Mr. Ulbricht’s lawyer, Joshua L. Dratel, in submissions to the judge last week, argued that Mr. Ulbricht’s website had been “far safer” than traditional street drug dealing, and that prosecutors could not prove a link between the site and the overdoses.
Mr. Dratel argued that deterrence would be “more than amply accomplished” by imposing the mandatory minimum 20-year term and that in any case, his client should receive a term “substantially below” the recommendation of the federal sentencing guidelines, which was that Mr. Ulbricht be sentenced to life.
Mr. Ulbricht, in a personal letter to the judge on Friday, said he had created Silk Road not for financial gain but because he believed “people should have the right to buy and sell whatever they wanted so long as they weren’t hurting anyone else.”
But he added that Silk Road “turned out to be a very naïve and costly idea that I deeply regret.”
Mr. Ulbricht, who did not testify at his trial, said that if he made it “out of prison, decades from now, I won’t be the same man, and the world won’t be the same place.”
“In fact, I’ll be an old man, at least 50, with the additional wear and tear prison life brings,” he wrote. “I will know firsthand the heavy price of breaking the law and will know better than anyone that it is not worth it. Even now I understand what a terrible mistake I made.”
The prosecutors, Serrin Turner and Timothy T. Howard, argued in their memorandum that Mr. Ulbricht’s website had “dramatically lowered the barriers to obtaining illegal drugs.”
“With the click of a mouse, a Silk Road user could circumvent all of the physical obstacles that might otherwise prevent or deter one from obtaining drugs locally,” the prosecutors wrote.
“Someone who might not know where to find drugs in his or her area, or feel comfortable searching them out, could find and buy drugs effortlessly on Silk Road,” the prosecutors said, adding, “The site provided a one-stop online shopping mall where the supply of drugs was virtually limitless.”
The defense’s submission to the judge included close to 100 letters written in support of Mr. Ulbricht, including some from people who had been jailed with him. The government said the judge should consider the letters but should also weigh them against the facts of Mr. Ulbricht’s criminal conduct: seeking “to profit from the drug abuse and addiction of others.”
Mr. Ulbricht, in his letter to Judge Forrest, pleaded for some leniency.
“I’ve had my youth, and I know you must take away my middle years, but please leave me my old age,” he said. “Please leave a small light at the end of the tunnel, an excuse to stay healthy, an excuse to dream of better days ahead and a chance to redeem myself in the free world before I meet my maker.”
A version of this article appears in print on May 27, 2015, on page A20 of the New York edition with the headline: Prosecutors Seek Long Prison Term for Creator of Illicit-Drug Website. Order Reprints| Today's Paper|Subscribe
The government, in a sentencing memo filed on Tuesday in Federal District Court, depicted the defendant, Ross W. Ulbricht, as a digital drug kingpin who ran an “online black market […]