One brick does not make a wall, but many bricks do.

When I was a federal prosecutor, a supervisor of mine frequently used this metaphor to remind us that one piece of evidence alone is rarely enough to prove a crime, but enough pieces of evidence are sufficient to prove guilt.

Michael Cohen’s public testimony on Wednesday did not constitute a wall of evidence, but it did provide several new bricks that could be used to build a case against President Donald Trump. Depending on other evidence in the hands of Special Counsel Robert Mueller, these pieces of evidence may be enough to prove Trump guilty of criminal or impeachable offenses.

Trump’s former lawyer testified about several facts that are significant bricks in the figurative wall of evidence.

First, Cohen testified that he was present when Trump spoke to Roger Stone on speakerphone in July 2016, when Stone said that he had talked to WikiLeaks founder Julian Assange about an upcoming “massive dump of emails that would damage Hillary Clinton’s campaign.” According to Cohen, this call came just days before the Democratic National Convention. If Cohen is correct on the timing, this event also occurred after the DNC had announced in June that it had been hacked by Russia, and so Russia’s involvement in the release would have been known by Trump. Cohen said that Trump responded by saying words to the effect of “wouldn’t that be great.”

Mueller has already charged 12 Russian intelligence officers with conspiring to defraud the United States by interfering with the fair administration of elections. As alleged, the objective of the conspiracy was to hack, steal, and stage the release of emails. If Mueller can establish that Stone, Trump, or others participated in the same conspiracy, such as by suggesting the timing of the release, then they could be properly charged as co-conspirators with the Russian intelligence officers.

Conspiracy requires more than mere knowledge that a crime is being committed. Conspiracy requires an agreement that some member of the group will violate the law and the commission of at least one overt act in furtherance of the agreement. The agreement may be explicit or implicit. Even encouragement can be an overt act. The call that Cohen says he heard between Trump and Stone alone does not establish that Stone and Trump participated in a conspiracy with the Russian hackers, but it is a piece of evidence, combined with other evidence, that could help establish sufficient evidence of a crime.

For instance, in the Stone indictment, Mueller alleges that sometime after July 22, 2016, “a senior Trump campaign official was directed to contact Stone about any additional releases and what other damaging information” WikiLeaks had about the Clinton campaign. The indictment goes on to allege that “Stone thereafter told the Trump campaign about potential future releases of damaging material by WikiLeaks.” Who has the authority to direct a senior campaign official other than an even more senior campaign official, or Trump himself? The call Cohen describes, along with the evidence behind the Stone indictment, may provide evidence of a crime or impeachable offense by Trump.

“ Trump’s alleged coaching of Cohen came in the midst of requests by Congress to Cohen and other Trump associates to produce records regarding contacts with Russia. ”

Second, Cohen testified that he recalled a time in June 2016 when Donald Trump Jr. entered his father’s office, walked around behind the desk, and told Trump in a low voice that “the meeting is all set.” According to Cohen, Trump replied, “OK good... Let me know.” The timing of this conversation coincided with the Trump Tower meeting between Trump Jr., Paul Manafort, Jared Kushner, and Russians to discuss “dirt” on Clinton. Cohen’s testimony about this conversation alone does not establish that Trump knew about the meeting with Russia or conspired with Russians to interfere with the election, but it provides one more piece of evidence that he did. Coupled with additional evidence, this testimony could amount to conspiracy to defraud the United States.

Third, Cohen testified that Trump’s personal lawyers “reviewed and edited” Cohen’s false 2017 testimony before Congress, in which Cohen has now admitted to lying that negotiations with Russia to build a Trump Tower in Moscow ended in January 2016, when, in fact, they continued until June 2016. Cohen further testified that between January and June, Trump asked him about the status of negotiations in Russia “at least a half-dozen times.”

In May 2017, Trump also allegedly said to Cohen that “there’s no business in Russia,” suggesting, perhaps, that Cohen should continue to support that lie. This testimony alone does not establish obstruction of justice against Trump, but it could be some evidence of such a crime. Trump’s alleged coaching of Cohen came in the midst of requests by Congress to Cohen and other Trump associates to produce records regarding contacts with Russia. If additional evidence can show that Trump encouraged Cohen to lie to Congress, with a corrupt intent to interfere with the investigation, then he could be charged with obstruction of justice, if not in an indictment, then in articles of impeachment.

One other topic unrelated to Russia may prove to be the most damning of all. Cohen testified that he paid off adult film star Stormy Daniels in the closing days of the campaign to maintain her silence about an affair with Trump. Cohen further testified that Trump directed Cohen to use his own personal funds to prevent the payment from “being traced back to him that could negatively impact his campaign.” This payment was the basis of a campaign finance violation to which Cohen pleaded guilty in the Southern District of New York. Cohen testified that Trump paid Cohen back with Trump’s own personal funds after Trump became president, and produced the check to support his testimony. For those who have argued that an impeachable offense must occur during the president’s term, the timing of this payment is significant because it means that Trump committed the offense while he was president.

Again, Wednesday’s testimony alone is not enough to convict or impeach Trump, but coupled with other evidence, such as recorded conversations that have been publicly disclosed or any supporting testimony from Trump Organization CFO Allen Weisselberg, it could be a significant piece of evidence of conspiracy to violate campaign finance laws.

Of course, Cohen’s credibility is questionable in light of his prior lies to Congress and other crimes, another reason that Cohen’s testimony alone will not be enough to charge or impeach Trump. But liars can be corroborated. Mueller would want to find other evidence to confirm Cohen’s testimony, such as phone records, bank records, intelligence intercepts, or the testimony of others. All of these pieces of evidence mean little when viewed alone, but when considered together, they may add up to a case against the president.

President Trump may get his wall built after all, just not the kind he had envisioned.