(ABC News) -- A change being proposed as part of an immigration reform bill in the Senate might have helped the U.S. keep a closer watch on one of suspects in the Boston Marathon bombings.
An immigration reform bill would mandate the creation of an electronic system to better track entries and exits at the country's airports and seaports. The U.S. currently uses a fingerprint system to record entries of non-U.S. citizens, but exits are monitored using a combination of government databases and airline flight logs. Under the new system, exits would also be tracked electronically using scanned passport data.
Here's why that's relevant to what happened in Boston:
Tamerlan Tsarnaev, who was killed in a firefight with law enforcement officers last week, traveled to Russia for six months in 2012. Federal authorities are now investigating that trip for any potential ties to the attack.
There's some confusion about whether the federal government knew about the trip to Russia, where Tsarnaev was reported to have visited his native Chechnya and Dagestan. The FBI had previously interviewed him at the request of the Russian government, and the suspect's name was then entered in a U.S.-government database used to screen airline arrivals.
Homeland Security Secretary Janet Napolitano testified at a Senate committee hearing on Tuesday that her department was aware of when Tamerlan Tsarnaev left the U.S., but not when he returned.
The FBI didn't know about the trip at all, according to Sen. Lindsey Graham (R-S.C.). He said that the airline Tsarnaev used, Aeroflot, misspelled his name when entering it in the flight manifest, preventing the agency from tracking him.
During the hearing on Tuesday, Graham said that he and Napolitano would need to further clear up the discrepancy between the two accounts.
Republican Sen. Chuck Grassley pressed Napolitano for more details later in the hearing, but she held back. "I think it would be better if we could discuss those with you in a classified setting."
During the hearing, Napolitano pointed out that the FBI was no longer investigating Tsarnaev by the time he returned. An FBI official told the AP that even if his name had been spelled correctly and his trip had been recorded properly, the FBI would not have had the authority to investigate any further because at that point it had found no terrorist links to Tsarnaev.
The bombings in Boston have shifted the focus of the immigration reform debate in Congress over the past week to a conversation about national security. Along those lines, Napolitano said at the hearing on Tuesday that adopting an electronic exit system and removing the element of human error that comes along with manually inputting flight logs would improve security overall.
While opponents of the bill have said the Boston attack raises doubts about the legislation, supporters are simultaneously stressing how immigration reform could help combat terrorist threats.
One of the congressman who drafted the Senate legislation, Sen. Charles Schumer (D-N.Y.), said at the hearing that passing reform would make the country safer:
"Under our bill everything would have to be passport or machine readable, so that type of mistake could not occur," Schumer said. "So if our bill were law, it could have been a pretty safe guess that the authorities would have known that Tsarnaev left to go to Russia and knew when he came back."
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