As the special counsel investigation nears its end, its most anticipated area of inquiry remains unresolved: Did the Trump campaign “collude” with Russia during the 2016 presidential election? Legally, the question of “collusion” has always been a question of conspiracy. Any potential charges related to Russian collusion would likely allege a conspiracy to violate one or more federal statutes, such as those prohibiting fraud against the United States, foreign campaign assistance, or computer hacking.

That Mueller has not yet alleged a Trump-Russia conspiracy, despite convicting several Trump associates for other crimes, has fueled speculation that the special counsel may lack sufficient evidence to bring collusion-related charges. NPR recently wrote that “an ostensible conspiracy between Trump’s campaign and the Russians who attacked the election is nowhere near close to being proven … From what we know today … the case is still Swiss cheese.” Others have expressed similar skepticism based on the publicly available evidence.

But is the current evidence of Russian collusion really so lacking? Does it matter from a legal perspective that there may not be a “smoking gun?” One might expect the answers to these questions to come from previous instances of foreign election-tampering or other geopolitical scandals. But much of the best guidance comes from a less obvious place: the corporate world of antitrust law.

Antitrust law’s relevance to the Russia investigation stems from the unique relationship that existed between Trump and Russia during the campaign, which was more akin to rival businesses accused of price-fixing than traditional criminal associates. Unlike in a typical criminal conspiracy, where participants conceal their actions because they are illegal regardless of any underlying conspiracy (think drug dealers or bank robbers), Trump’s support for Russia’s policy objectives during the race was public and ostensibly legal so long as it was undertaken independently. From a conspiracy perspective, it was not illegal, standing alone, for the Trump campaign to meet with Russian agents, advocate easing Russian sanctions or dismantling NATO, negotiate a Trump Tower in Moscow, or publicly request that Russia locate Hillary Clinton’s emails.

But if Trump’s support for Russia was part of a coordinated effort through which Trump engaged in pro-Russian advocacy in exchange for prohibited electoral or financial assistance—something that is far from proven—that could form the basis of an illegal conspiracy. The key to proving such a conspiracy would be to show that Trump and Russia formed a “unity of purpose, or common design and understanding, or a meeting of minds”—the legal test for establishing the “agreement” prong of a conspiracy.

This task that Mueller now faces—determining whether supposedly unilateral, lawful actions were actually the result of a covert agreement—is the defining feature of an entire other area of the law: price-fixing conspiracies. For more than a century, antitrust prosecutors and litigators have similarly sought to prove the existence of secret collusion between rivals. The body of conspiracy law that has developed in the antitrust context is among the most robust in all of American jurisprudence and applies with similar force to non-antitrust conspiracies. It offers the best road map for evaluating the Russia investigation as it reaches its final stages.

So what does antitrust law teach us about allegations of Russian collusion? From what we know today, and contrary to partisan narratives, the applicable legal framework yields no clear outcomes for either side. It offers equal defenses to Trump as it does ammunition to Mueller.

First, Mueller will not need to show direct evidence of a Trump-Russia agreement to prove a conspiracy. Because antitrust conspiracies, like a potential Trump-Russia conspiracy, are carried out by sophisticated actors adept at avoiding detection, courts have ruled that “it is well recognized law that any conspiracy can ordinarily only be proved by inferences drawn from relevant and competent circumstantial evidence.” Courts have explained that “[b]y its nature conspiracy is conceived and carried out clandestinely, and direct evidence of the crime is rarely available.”

The ability to prove a conspiracy without direct evidence of an agreement is not just theoretical.

Second, Mueller will not need to show that a “formal agreement” existed between Trump and Russia. Nor, according to precedent, must he show that Trump and Russia “met each other” or “stated in words or writing what the scheme was or how it was to be effected.” All Mueller would need to show is that Trump and Russia “tacitly came to a mutual understanding,” something that can occur without personal communication or a clear quid pro quo. Courts have long recognized that a “knowing wink can mean more than words” and that a conspiracy can be proven through “a course of dealing or other circumstances,” just as it can through express communication.

The ability to prove a conspiracy without direct evidence of an agreement is not just theoretical. The government has successfully prosecuted antitrust conspiracies using circumstantial evidence in the past. In one example, competing lumber companies were convicted of conspiring to rig lumber purchases by agreeing in advance about which companies would bid on which sales. There was no direct evidence that the companies reached an agreement to coordinate their bids, but there was evidence showing that they met to discuss which sales each company found desirable and thereafter avoided competing on those sales. Despite the lack of direct evidence of an agreement, the trial court held there was sufficient evidence of an “implied agreement.” The appellate court affirmed, finding that there was “no doubt” the companies had reached an “understanding” on bidding.

The types of circumstantial evidence from which juries may infer agreements from such conduct—known in the antitrust world as “plus factors”—overlap in part with what is publicly known about potential collusion with Russia. Plus factors arise when alleged co-conspirators (1) share motives to conspire; (2) had secret contacts with no legitimate purpose; (3) made suspicious changes in behavior following such contacts; and (4) sought to conceal their contacts through pretexts and false denials. Without direct evidence of an agreement, prosecutors will need to establish enough plus factors to eliminate any doubt that Trump and Russia reached an agreement.

At present, certain aspects of their case appear stronger than others.

One threshold showing that prosecutors could likely make is that Trump and Russia had motives to conspire. Trump was losing in the polls throughout the campaign, and his staff knew that Russia possessed something that could help swing the election in his favor: thousands of hacked emails supposedly implicating Hillary Clinton. Trump was also negotiating with the Kremlin over a potentially lucrative Trump Tower in Moscow, and his campaign manager was seeking to use his position to repay millions of dollars in debt to prominent Russians. Meanwhile, Russia was seeking relief from the Magnitsky Act sanctions supported by Trump’s political opponents and derided Clinton for her vocal criticism of Russia. To prove a conspiracy, though, prosecutors must do more than merely show these motives existed; they must show Trump and Russia agreed to act on them.

Stronger, yet still inconclusive, evidence of an agreement lies in the numerous contacts between Trump associates and Russians during the campaign. The most famous contact was a June 9, 2016 meeting at Trump Tower between Kremlin-connected Russians and Trump’s top campaign staff. The meeting was organized by an intermediary who claimed that Russians could provide damaging information on Clinton as part of “Russia and its government’s support for Mr. Trump.” Donald Trump Jr. responded that he “love[d]” the idea, one that echoed what a Kremlin-linked professor had told campaign adviser George Papadopoulos a month earlier about Russia possessing thousands of hacked Democratic emails. At the meeting, the Russians requested an end to the Magnitsky Act sanctions, and Trump Jr. indicated they would revisit the topic if Trump won the election. That same day, in what may or may not have been a coincidence, Trump’s personal lawyer Michael Cohen began arranging travel to St. Petersburg to meet with Putin’s inner circle regarding the Trump Tower Moscow project. And just five days later, Russian military hackers began publicly releasing the first wave of stolen Democratic emails.

Trump’s support for Russia, meanwhile, continued as the campaign progressed. In July 2016, the Trump campaign reportedly intervened to prevent anti-Russia language from being included in the GOP platform after several meetings with Russian Ambassador Sergey Kislyak. Then, on the same day that Trump publicly encouraged Russia to locate more Clinton emails, Russians attempted for the first time to hack Clinton’s personal email account. Throughout the fall, Trump associate Roger Stone was secretly communicating with Russian hackers and WikiLeaks about stolen Democratic emails. And after Trump won the election, his transition team sought to establish a secret back channel with Russia and covertly persuaded the Kremlin to avoid retaliating for sanctions imposed under the Obama administration. Antitrust law dictates that such changes in behavior support an inference of conspiracy when they follow defendants’ secret contacts.

If presented at trial, the jury’s task will be to determine whether this mutual assistance between Trump and Russia reflects mere parallel conduct (i.e., pursuing similar goals without coordination), which is not itself illegal—or coordinated conduct, which is.

The key burden for the prosecution, as antitrust law dictates, will be to show that Trump and Russia did more than merely anticipate one another’s interests and pursue them independently. Such “conscious parallelism,” as it is known in antitrust law, is not sufficient to show a conspiracy. This is because distinct actors can share and pursue the same goals without necessarily agreeing to do so.

This is where the prosecution’s case shows signs of weakness. Absent additional evidence, Trump could plausibly argue that while he knew Russia was interfering in the election and seeking sanctions relief, his support for Russia did not stem from any arrangement, but rather from his own rational belief that supporting Putin might spur further election assistance. Problematic as this may be, it is not sufficient to establish a conspiracy.

This “conscious parallelism” defense, common in price-fixing cases, could be a successful defense for Trump. With what we know today, Russia and Trump’s conduct can be rationally explained without concerted action. Russia has intervened in several foreign elections, and Trump began showing favoritism toward Russia long before his campaign began. It is possible this dynamic progressed during the campaign without any coordination between the two sides.

To overcome such a defense, prosecutors would need to show that Trump and Russia reached some semblance of an actual agreement, which the law defines flexibly as “a unity of purpose or a common design and understanding, or a meeting of minds.” Without direct evidence of an agreement, prosecutors’ best argument will be that coincidence and parallel thinking alone could not have yielded the high degree of parallel conduct that Trump and Russia exhibited, particularly when their secret contacts provide a more rational explanation for their mutual support. Plaintiffs in civil antitrust conspiracy cases often make similar arguments with success.

Trump and Russia’s public statements could also provide circumstantial evidence of an agreement.

Crucially for Trump, this argument will hold less sway in a criminal case, where prosecutors have the burden of proving an agreement beyond a reasonable doubt. If after all the evidence is presented, Trump can offer a plausible explanation for his conduct that does not involve an agreement with Russia, prosecutors will have failed to “exclude the possibility” that Trump and Russia acted independently, making a conviction unlikely. To avoid this, Mueller will need enough circumstantial evidence to eliminate any non-collusive explanations for Trump’s conduct, including the possibility that Trump and Russia acted “consciously parallel.” Doing so will require more evidence that what is publicly known today.

This is not to suggest that the present information is irrelevant to prosecutors. Trump and his associates’ attempts to cover up their Russian contacts bolster the prosecution’s case. Among other things, Trump repeatedly denied his campaign’s extensive meetings and communications with Russians and personally dictated a misleading statement about the June 2016 Trump Tower meeting. Antitrust law holds that such false denials raise an inference of conspiracy and tend to “disprove the likelihood of independent action.”

Trump and Russia’s public statements could also provide circumstantial evidence of an agreement. It is no defense that Trump and Russia may have communicated through the media and public speeches rather than through covert channels. Antitrust law recognizes that such public “signaling” can also facilitate conspiracies because conspirators can use public means to reach agreement just as they can private ones.

Those weighing the evidence should ultimately keep three things in mind. First, federal guidelines recommend bringing charges if admissible evidence will “probably” be sufficient to obtain and sustain a conviction—meaning if there is a greater than 50 percent chance of winning at trial. Second, the jury’s duty is to consider evidence of a conspiracy “as a whole,” without “tightly compartmentalizing the various factual components and wiping the slate clean after scrutiny of each.” Third, if the redactions in Mueller’s legal filings suggest anything, it is that there may be substantially more evidence implicating Trump than what has been publicly released to date, only a portion of which has been described here.

Whether Mueller will ultimately bring conspiracy charges against Trump and his associates is a complicated calculus involving an unparalleled mix of evidentiary, political, and constitutional considerations. Antitrust law provides little guidance on how Mueller might proceed on those fronts. But anyone making assurances at this stage reveals more about their ignorance of the law than their knowledge of the case. The more insightful dialogue we should be having as we await Mueller’s findings has less to do with the investigation’s outcome than the legal principles shaping its path and how those principles apply to the still-developing body of evidence.

On this question, we may soon get a preview. Last year, the Democratic National Committee filed a civil lawsuit alleging a wide-ranging conspiracy between the Trump campaign, Russia, WikiLeaks, and others to use stolen DNC emails to assist Trump’s candidacy. Substantive briefing in the case could begin later this year. While the DNC’s case is narrower than Mueller’s inquiry, the legal arguments raised in the civil case may foreshadow each side’s arguments in a potential criminal one. The key inquiry in both cases will be the same: Is there sufficient evidence of an agreement between Trump and Russia to establish a conspiracy? No area of law is better equipped to answer this question than antitrust law. Expect it to figure prominently as both cases unfold.