Asked about the microwave theory of the case, the State Department said the investigation had yet to identify the cause or source of the attacks. And the FBI declined to comment on the status of the investigation or any theories.
The microwave idea teems with unanswered questions. Who fired the beams? The Russian government? The Cuban government? A rogue Cuban faction sympathetic to Moscow? And, if so, where did the attackers get the unconventional arms?
Could these microwave weapons be in use now, and are certain individuals feeling the effects of these weapons?
Early this year, in January, the spooky impact of microwaves on the human brain never came up during an open Senate hearing on the Cuban embassy attack.
But in a scientific paper that same month, James C. Lin of the University of Illinois, a leading investigator of the Frey effect, described the diplomatic ills as plausibly arising from microwave beams. Dr. Lin is the editor-in-chief of Bio Electro Magnetics, a peer-reviewed journal that explores the effects of radio waves and electromagnetic fields on living things.
In his paper, he said high-intensity beams of microwaves could have caused the diplomats to experience not just loud noises but nausea, headaches and vertigo, as well as possible brain-tissue injury. The beams, he added, could be fired covertly, hitting “only the intended target.”
In February, ProPublica in a lengthy investigation mentioned that federal investigators were weighing the microwave theory. Separately, it told of an intriguing find. The wife of a member of the embassy staff, it reported, had looked outside her home after hearing the disturbing sounds and seen a van speeding away.
A dish antenna could fit easily into a small van.
The medical team that studied the Cuba diplomats ascribed the symptoms in the March JAMA study to “an unknown energy source” that was highly directional. Some personnel, it noted, had covered their ears and heads but experienced no sound reduction. The team said the diplomats appeared to have developed signs of concussion without having received any blows to the head.
Reports emerged that American diplomats in China had suffered similar traumas. Secretary of State Mike Pompeo called the medical details of the two groups “very similar” and “entirely consistent” with one another. By late June, the State Department had evacuated at least 11 Americans from China.