The docket of Judge Jack Weinstein in Brooklyn has long been a magnet for big lawsuits with billions of dollars at stake. In case after case involving guns, cigarettes, Agent Orange, breast implants, typing keyboards, asbestos, and pharmaceuticals, manufacturers have defended their products before the now 86-year-old federal judge.

Around the courthouse, Judge Weinstein is best known for his unpretentious courtroom manner — he rarely wears a robe and addresses convicted murderers with the same courtesy he extends toward partners at major law firms. Across the country, the judge is known for having “a big strike zone” for plaintiffs, according to an expert in mass torts, David Herr, a Minneapolis attorney. Judge Weinstein’s willingness to shepherd class actions built on novel legal theories toward trial has made him a hero to trial attorneys and a foe to corporations.

The latest interest in Judge Weinstein doesn’t stem from any of his Page 1-worthy rulings but the more arcane question of how some of his cases got assigned to the judge in the first place. At issue is how more than a dozen lawsuits brought against the tobacco industry — and several suits against firearm manufacturers — ended up before the judge.

By and large, these suits, about 20 in all, against the tobacco and firearm industries didn’t arrive on Judge Weinstein’s docket through a “spin of the wheel” — the random case assignment process by which suits are sent to judges. Instead, plaintiffs in the know have long used an administrative shortcut to maneuver lawsuits against the same set of defendants into the courtroom of their choice. Their choice is often Judge Weinstein.

In response, defense attorneys for the firearm and tobacco industries have alleged judge shopping and long tried to get their cases yanked from Judge Weinstein’s courtroom and reassigned, with mixed results. On Thursday, the issue will come again to a head when a lawyer who has long represented the firearm industry, John Renzulli, will ask Judge Weinstein to recuse himself from a high-profile gun suit. The case was brought by New York City against out-of-state gun dealers who have sold handguns later recovered at crime scenes in the city.

It isn’t the first time Mr. Renzulli has made this sort of motion — that was back in 1996. In the meantime, Judge Weinstein’s docket has drawn increasing scrutiny. There’s even a judge on the 2nd Circuit, Jose Cabranes, who makes a habit of quizzing lawyers about the matter when Judge Weinstein’s rulings come up on appeal. “Is there a rule or practice in the Eastern District of New York that Judge Weinstein is assigned to all mega-cases?” the Judge Cabranes asked several years ago. The comments came during oral arguments reviewing Judge Weinstein’s decision to try a case brought by Blue Cross and Blue Shield against the tobacco industry. The question has stuck with Judge Cabranes over the years. This September, he asked why the city’s lawyers had taken a suit against firearm manufacturers “across the Brooklyn Bridge” to where Judge Weinstein sits, when the court in Manhattan was nearer to the city’s law offices.

Plaintiffs have a good chance of picking which judge will hear their case simply by checking off a box. When filing a case in federal court, plaintiffs can indicate that their case is “related” to another case already in the court. The new case is then automatically assigned to that judge, instead of being randomly assigned.

The firearm and tobacco suits in Judge Weinstein’s courtroom are there because plaintiffs have said they were related to earlier tobacco and firearm suits that Judge Weinstein has handled. This practice was first reported in a National Law Journal article from 1999. The first tobacco case Judge Weinstein heard ended up before the judge because of his involvement in asbestos litigation, according to one lawyer. That suit was on behalf of the Manville Trust, which was established for those with asbestos-related illnesses. Judge Weinstein had previously been involved in overseeing the trust. When the trust sued tobacco companies in 1999 on the theory that they were responsible for some of the respiratory illnesses among asbestos workers, the plaintiffs indicated that the case was related to the earlier litigation, the lawyer who filed the suit, James Stengel of Orrick, Herrington & Sutcliffe, said in an interview.

The first industry-wide suit against firearm manufacturers for negligent marketing to arrive before Judge Weinstein in 1995 had been marked down as related to two earlier cases, one from about 15 years earlier. One of cases claimed that the trigger pull on a shotgun had been too light. The other case was against manufacturers of the drug DES, which was once prescribed to prevent miscarriages, and involved a similar theory of market share liability as the firearm litigation. Lawyers for the firearm companies have long claimed that the lawyer who filed the suit had stretched the related case rule so that Judge Weinstein would get the case.

Since then, “the assignment of this entire chain of firearms cases to Your Honor can only be characterized as a poisonous tree,” Mr. Renzulli, the firearms lawyers, wrote this month to Judge Weinstein. “The misuse of the assignment process is wholly improper.” The related case rule is designed to prevent a whole slate of judges from reviewing the same evidence in a series of similar suits against the same defendants.

“The related case rule is a good thing,” the lawyer who filed the gun suit in 1995, Elisa Barnes, said, “because judges are completely busy and there is insufficient time for every judge to learn all there is to be learned on complex issues.”

Ms. Barnes cautioned against ” jumping to the completely erroneous opinion that Judge Weinstein is completely for the plaintiffs.” She noted his dismissal of her later lawsuit on behalf of the NAACP against gun manufacturers.

So far none of the juries in the two trials against the firearm industry and one trial against cigarette makers that have occurred in Judge Weinstein’s courtroom have leveled a significant award against either industry.

If there is some disagreement on how plaintiffs have actually fared before Judge Weinstein, there is little dispute that the related case rule has given a single judge an outsize influence in lawsuits against the tobacco and firearm industries. Because of Judge Weinstein’s presence, the U.S. Courthouse in Brooklyn has become the focal point of litigation against those two industries — even though no major manufacturer in either industry is headquartered in the borough and the alleged harms are generally nationwide.

One of the country’s top tobacco lawyers, Theodore Grossman, described the moment when he realized that the system for how judges are assigned to cases “had broken down.” He was in Los Angeles for a deposition of the lead plaintiff in the “Simon II” tobacco litigation — in which Judge Weinstein certified a class of nationwide smokers seeking punitive damages. The lead plaintiff was Californian, his lawyer was Tennessean, and Mr. Grossman was representing R.J. Reynolds, whose headquarters are in North Carolina.

“This was for a case brought in the Eastern District of New York,” Mr. Grossman, who is with the Cleveland office of the firm Jones Day, said. “And the only reason the case had been brought there was to have the case before the chosen judge.”

Asked how so many major cases ended up on his docket, Judge Weinstein said in an interview, “I’m lucky.”

“We don’t reach out for cases, we wait until they come to us,” he said.

Judge Weinstein said some of his largest cases, such as ongoing suits over the defoliant Agent Orange and an anti-psychotic drug, Zyprexa, first came to him via the court in Washington, D.C., that assigns multi-district litigation. He said that to the best of his recollection, the first gun case and tobacco case that he handled came to him through the wheel.

At times, Judge Weinstein has let some cases go. Just last year, Judge Weinstein approved Philip Morris’s request that a suit demanding the company pay the medical monitoring of smokers be reassigned to another judge. Philip Morris had argued that beyond the subject matter of cigarettes, the case involved “different parties, different causes of action, different facts, different expert evidence, and different legal questions” from the other tobacco cases already before the judge.

At other times, Judge Weinstein has referred motions for his recusal to other judges. In one instance, another judge, Eugene Nickerson, ruled that defendants didn’t have standing to litigate over a related case designation, because it was merely an administrative tool for the court’s benefit.

Another judge, faced with deciding a motion to reassign one of Judge Weinstein’s tobacco cases, in 1999 wrote that “the inference that plaintiffs have ‘judge-shopped’ in this case is neither overwhelming nor inescapable.” The judge, Charles Sifton, said many of the tobacco suits being filed as “related” did indeed rely on the same evidence — such as records of meetings between tobacco executives — as other cases Judge Weinstein had before him. There are signs that other judges are concerned that plaintiffs have steered cases towards Judge Weinstein. At a 2004 memorial service for Judge Jacob Mishler, one former colleague, Judge George Pratt, had some unusual praise for the deceased. With Mishler, there were “no manipulations of the related-case rule,” he said.

Judge Pratt, who is retired from the bench and in private practice, declined to talk about his comments. Two people present said those remarks can only be interpreted as a swipe at Judge Weinstein.