An FBI analysis of crudely made pipe bombs mailed to prominent critics of President Donald Trump has concluded they wouldn't have worked.

A January report on the analysis was filed in Manhattan federal court Tuesday.

The FBI said the devices wouldn't have functioned because of their design, though it couldn't be determined whether that was from poor design or the intent of the builder.

It said the fusing system for each device lacked the proper components and assembly to enable it to function.

Cesar Sayoc faces a mandatory 10-year prison term and up to life for mailing the packages out to Democrats, including Sen. Cory Booker. Sayoc also sent a package to CNN’s headquarters.

The Florida man says that he never intended to hurt anyone when he sent the packages out around the midterm elections. He pleaded guilty to explosives-related charges in March.

Sayoc will be sentenced in September.