A row has broken out over whether the Obama Administration is violating the legal due process of Boston terror suspect Dzhokhar Tsarnaev by not reading him his Miranda rights before questioning. The more relevant question for the safety of the U.S. homeland is why the Administration has declined to designate him as a terrorist enemy combatant.

With Dzhokhar wounded and in custody and his brother Tamerlan dead, the focus is shifting to how the brothers became radicalized and whether they had links to foreign or domestic terror networks. It's becoming clearer by the day that elder brother Tamerlan had become increasingly religious and that his motive last week was Islamic jihad against America.

U.S. officials say he spent months overseas in 2012, including time in Chechnya. Media reports say the FBI questioned him after a warning from a foreign intelligence service (presumably Russia's). Yet the FBI appears not to have kept an eye on him, though media reports now say that within a month of returning from Russia he was posting jihadist videos on websites.

The FBI has some explaining to do, and more than merely claiming that it can't track everyone who pops up on a foreign intelligence list. One question is whether anyone in government requested that the federal FISA court issue a warrant so Tamerlan could have his Web postings or phone calls surveilled electronically. This doesn't mean G-men in a car following him 24-7. It means putting him into a National Security Agency program so that pro-jihad postings would be noticed.

FBI officials were clearly major sources for the Associated Press stories in 2011 that attacked the New York Police Department for its antiterror surveillance program, in part for reasons of bureaucratic competition. But in the Boston case, we only wish the NYPD had been in charge. Instead the FBI interviewed Tamerlan, then apparently lost interest or focus even as he was showing signs of radicalization, so the homegrown jihadist was able to engineer the most successful terror attack on U.S. soil since 9/11.