The investigation: How did the FBI miss Omar Mateen?

If you follow social media on the topic of the FBI and terrorism, you will find two themes predominate whenever a terrorist incident occurs in the U.S. The first is promulgated by conspiracy theorists, anti-law-enforcement social activists and progressive-minded publications that assert that the FBI manufactures terrorism-related crimes to entrap innocent individuals — primarily young Muslims. These are crimes that would-be terrorists are incapable of committing on their own, they say, without the help of an FBI informant or undercover agent. In these scenarios, the FBI leads the poor, unsuspecting proto-terrorist by the hand through the various stages of planning, commitment, obtaining a weapon of mass destruction and, ultimately, pulling the fake trigger. When the proto-terrorist is finally arrested, certain segments of the public, press and pundits howl about how the FBI abused its power and authority to railroad an innocent person.

The second theme that predominates is usually something like this: "If you knew about this terrorist and investigated him, why wasn't he arrested and this horrible act prevented?" This theme was played over and over again during the Boston Marathon bombing investigation when it was revealed that Russian police had sought information from the FBI on Tamerlan Tsarnaev's activities in America. Many people thought the FBI should have continued to investigate Tsarnaev until the Boston plot was uncovered. Of course, this is never as simple as it seems — the FBI does not have free rein in a domestic terrorism investigation.

The same arguments are now again ringing out with the revelation that the FBI investigated Orlando shooter Omar Mateen — not once, but twice — over the past several years for terrorism-related associations. Like Tsarnaev, Mateen wasn't arrested, and both cases were closed for lack of evidence of a crime.

Is this because the FBI is bad at investigations? Or maybe it's because unless the FBI is playing puppet-master, it's incapable of developing the evidence needed to investigate a potential terrorist? As the former head of the Seattle-based Puget Sound Joint Terrorism Task Force (JTTF), I know firsthand that neither of these assertions is true. Literally hundreds of assessments, preliminary inquiries and full investigations are opened each year by the FBI with the intent of preventing a terrorist attack. But many other cases were not investigated simply because under the current Domestic Investigations and Operations Guide, the FBI lacked probable cause to continue.

The fact is that the FBI's ability to investigate any case is limited by the requirements of probable cause to open a full investigation, which stem from the Fourth Amendment to the Constitution. Probable cause is a belief based upon articulable facts that would lead a reasonable person to believe an individual has committed, or intends to commit, a crime. It is the standard from which all coercive police powers stem in the U.S. Without probable cause based on fact, the FBI cannot open a case, execute a search warrant or take other appropriate law enforcement action. Both of Mateen's investigations were closed when the FBI determined that he had committed no crime and that he had no verifiable intent to commit one in the future. That would have required an overt act on the part of Mateen. But he remained a person of interest to many who knew him, including co-workers and associates.

Lack of probable cause is an important factor. It was one element that prevented the FBI from connecting the dots of the 9/11 plot. Zacarias Moussaoui was reported as wanting to learn to fly a jumbo jet, but not wanting to learn to take off or land, alarming his instructors. These suspicions alone, however, were not enough to enable the FBI to obtain a Foreign Intelligence Surveillance Court search warrant of his computer, which might have turned up evidence of the plot. Because of the Moussaoui case, the Syed Farook and Tashfeen Malik case in San Bernardino, Calif., and now the Mateen case, some argue that it may be time to lower the probable-cause threshold in terrorist cases, especially when the Islamic State in Iraq and the Levant (ISIL) has so brazenly called for attacks on American civilian targets. On the other hand, staunch supporters of privacy and constitutional limitations on police power argue that nothing justifies changing the standard, arguing that those who compromise privacy for safety have neither. The problem is, as we have seen in Orlando, the price paid for missing these investigative opportunities is high.

So why was it so hard to develop probable cause to believe that Mateen had committed or was about to commit a crime? According to the Washington Post:

The FBI said Sunday that Mateen had been investigated on two different occasions by the bureau. In both cases, he was interviewed by agents. In 2013, he was investigated for "inflammatory comments … alleging possible ties to terrorists," said Ron Hopper of the FBI. Mateen was investigated again the following year for possible connections to Moner Mohammad Abu-Salha, the first American to carry out a suicide attack in Syria. (Mateen and Abu-Salha had both lived in Fort Pierce, Fla.) The FBI ultimately was not able to substantiate the 2013 claims and deemed the relationship with Abu-Salha "minimal," saying there was no threat.

Some reasons for the closing of both cases stem from internal restrictions on FBI investigations. The FBI is precluded from opening an investigation on individuals solely based on their free speech. That is, no full investigation can be opened or continued merely on what people say, even if what they say is to pledge support for a terrorist group like ISIL. The only thing the FBI can do is conduct a limited review of public and FBI records and interview the subject. Extraordinary investigative techniques like wiretaps, undercover operations and targeting by an informant are restricted absent probable cause for a full investigation.

Another reason may stem from the FBI's recent struggle with Apple over access to Farook's iPhone. If Farook had been in contact with the Paris terrorists before the San Bernardino attack, and his communications monitored, this attack may have been prevented. While the National Security Agency closely monitors many jihadist internet boards, some communications remain encrypted beyond even their capabilities.

Future investigation will reveal whether or not Mateen used encryption or encrypted social media sites to communicate with ISIL, which has now claimed credit for the attack. Only time will tell. Yet, many still argue that the privacy and encryption rights trump saving human life. I believe that breakable encryption is the key to defeating ISIL and domestic terrorists, just as it was during World War II in both the European and Pacific theaters of war. We need to enhance the FBI's ability to proactively obtain communications from suspected terrorists, subject to court-ordered monitoring under the Foreign Intelligence Surveillance Act.

There are many valid legal, constitutional and privacy arguments for maintaining strong restrictions on the FBI's ability to investigate terrorism. The strongest often come from the conservative political right as well as from the progressive left. But as more terrorists become successful in hiding from the FBI in plain sight using encryption and other means, perhaps it is time to revisit the probable-cause standard to open investigations in potential terrorism cases.

It's too late for the Orlando victims, but a future change in what allows for opening a full FBI investigation may assist in preventing future acts of terrorism. Perhaps it is time for a return to the pre-9/11 standard for investigating terrorists — particularly if the need for the prevention of terrorist acts in the homeland is how the FBI is going to be judged in the future.

David Gomez is a former FBI counterterrorism executive in Seattle and current senior fellow at the George Washington University Center for Cyber and Homeland Security. He consults on operational and information security as a security strategist. He wrote this article for Foreign Policy magazine.