In the year since the assault on the Capitol by a pro-Trump mob, more than 700 people have been arrested, with little public indication from the Justice Department of how high the investigation might reach.By almost any measure, the criminal investigation of the Jan. 6 attack on the Capitol is a prosecutorial effort of unparalleled complexity and scope.For an entire year, federal agents in almost every state have been poring over mounting stacks of tipster reports, interviews with witnesses, public social media posts and private messages obtained by warrants. They have also collected nearly 14,000 hours of video — from media outlets, surveillance cameras and police-worn body cameras — enough raw footage that it would take a year and a half of around-the-clock viewing to get through it.While the Justice Department has called the inquiry one of the largest in its history, traditional law enforcement officials have not been acting alone. Working with information from online sleuths who style themselves as “Sedition Hunters,” the authorities have made more than 700 arrests — with little sign of slowing down.The government estimates that as many as 2,500 people who took part in the events of Jan. 6 could be charged with federal crimes. That includes more than 1,000 incidents that prosecutors believe could be assaults.As of this week, more than 225 people have been accused of attacking or interfering with the police that day. About 275 have been charged with what the government describes as the chief political crime on Jan. 6: obstructing Congress’s duty to certify the 2020 presidential vote count. A little over 300 people have been charged with petty crimes alone, mostly trespassing and disorderly conduct.But a big question hangs over the prosecutions: Will the Justice Department move beyond charging the rioters themselves?So far, the department has provided no public indication of the degree to which it might be pursuing a case against former President Donald J. Trump and the circle of his allies who helped inspire the chaos with their baseless claims of election fraud. Attorney General Merrick B. Garland is scheduled to give a speech on Wednesday, one day before the anniversary of the attack on the Capitol, but is not expected to provide any signals about the direction of the department’s investigation. A spokeswoman said he would not address any specific cases or individuals.On Capitol Hill, the House select committee on Jan. 6 is interviewing witnesses and has issued subpoenas to a number of high-profile figures allied with Mr. Trump. And with Mr. Garland and the Justice Department remaining mum about their intentions, members of the committee have signaled a willingness to exert pressure on the department, saying they would consider making criminal referrals if their investigation turns up evidence that could support a prosecution against Mr. Trump or others.Even the prosecutions of those who rioted at the Capitol have presented an array of moral and legal challenges that have bedeviled judges, prosecutors and defense lawyers.Overworked courts have tried to balance the laborious exchange of discovery materials with speedy trial protections and to manage the bleak conditions at Washington’s local jails where some defendants are being held without bail. They have also faced a fundamental, underlying tension: how to mete out justice on an individual level to hundreds of defendants who together helped form a violent mob.Jacob Chansley, the so-called QAnon Shaman, was sentenced to 41 months.Erin Schaff/The New York TimesPleas and SentencesWith rare speed for a large-scale prosecution, more than 160 people — or slightly more than 20 percent of all who have been charged — have pleaded guilty at this point. Of those, not quite half have already been sentenced.A few weeks ago, Robert Palmer, a Florida man who hurled a fire extinguisher at police officers, was sentenced to more than five years in prison, the longest term handed down so far. In November, one of the most familiar figures in the attack — Jacob Chansley, the so-called QAnon Shaman, who breached the Senate floor in a horned helmet with a fur draped over his shoulders — was sentenced to 41 months, a term he is appealing.Beneath the headlines, however, there has been a steady stream of penalties for lower-profile defendants: bricklayers, grandmothers, college students, artists, church leaders and long-haul truckers who, by and large, have admitted to little more than illegally entering the Capitol.Many, if not most, have avoided incarceration, sentenced to probation or stints of home confinement. Others have received only modest sentences, ranging from a few weeks to a few months.In court, those accused of minor crimes have almost always expressed remorse, saying their behavior was foolish, embarrassing or out of character. Some have broken into tears or, in one case, physically collapsed. Others have vowed never to attend a political rally again.Federal judges have taken slightly different positions on how to punish the defendants. Judge Trevor N. McFadden, appointed by Mr. Trump, often prefaces his sentences by calling the events that day “a national embarrassment” — though he has frequently declined to jail petty offenders. Judge Tanya S. Chutkan, an Obama appointee, has often given sentences higher than those requested by the government. Her go-to phrase: “There must be consequences.”Judge Amit P. Mehta told John Lolos, a defendant clearly steeped in election fraud conspiracies, that not only had he been lied to, but those who had done the lying were not “paying the consequences.”“Those who orchestrated Jan. 6 have in no meaningful sense been held accountable,” said Judge Mehta, another Obama appointee. “In a sense, Mr. Lolos, I think you are a pawn.”Prosecutors are using an unusual law to charge many of the rioters: the obstruction of an official proceeding before Congress.Pool photo by Erin SchaffLegal ChallengesFrom the start, prosecutors faced a unique legal problem: Never before had members of Congress been forced from the House and Senate floors while finalizing the transition of presidential power. What law should be used to charge this crime?The government settled on an unusual obstruction law — the obstruction of an official proceeding before Congress. It brought the charge against scores of people believed to have disrupted the democratic process, often alongside more traditional counts of trespassing, vandalism and assault.The obstruction law, which carries a maximum penalty of 20 years in prison, had a few advantages. First, it allowed the authorities to avoid deploying more politically fraught — and harder-to-prove — counts like sedition or insurrection.It also permitted prosecutors to home in on the specific behavior of defendants and judge how much their actions contributed to the chaos that day. If someone went deep into the Capitol, say, or took some other action that helped to chase officials from their duties, chances are they have been charged with an obstruction count.But many defense lawyers have claimed the law was wrongly used.Passed in 2002 as part of the Sarbanes-Oxley Act, which sought to clamp down on corporate malfeasance, the measure was initially intended to prohibit things like shredding documents or tampering with witnesses in congressional inquiries. Defense lawyers have argued that prosecutors have stretched the law beyond its scope and used it to criminalize behavior that too closely resembles ordinary protest protected by the First Amendment.In the past few weeks, however, five federal judges have ruled that the law is valid, and it now seems certain it will be permitted in scores of Jan. 6 prosecutions, including some that will soon go to trial.More than 160 people have pleaded guilty so far to charges stemming from the riot. The first trials are scheduled to begin in February.Erin Schaff/The New York TimesTrials to Begin SoonThe earliest Capitol riot trials are scheduled to begin next month. When the proceedings start, jurors will most likely get a glimpse of how the government believes members of the mob worked together.The first trial, set to begin on Feb. 24, will focus on Robert Gieswein of Colorado, a self-proclaimed militiaman charged with assaulting officers with a chemical spray.Key Figures in the Jan. 6 InquiryCard 1 of 10The House investigation. More