Illegal immigrants file into a U.S. Border Patrol facility in Tucson, Ariz. (Associated Press)

(CNSNew.com) – In the midst of the summer recess, Sen. Chuck Grassley (R-Iowa) issued a press release on Aug. 21 concerning a letter he wrote to the Department of Homeland Security seeking details about the release of 36,007 illegal aliens last year who had been convicted of a crime and were released by Immigration and Customs Enforcement (ICE) while awaiting deportation proceedings.

The June 9 inquiry, addressed to DHS Secretary Jeh Johnson, led to the revelation that of those thousands released, 169 had been convicted of “homicide-related” offenses.

“The public needs to know when a person is in the country illegally, and who has been convicted of a homicide, is released into their communities,” Grassley said in the press release.

Along with the letter, Grassley posted ICE’s response, which confirmed its release of 169 illegal aliens in fiscal year 2013 who had been convicted of “homicide-related” crimes.

The ICE response said that more than 130 zip codes in the U.S. were “associated with the detainees.”

Jessica Vaughn, director of policy studies at the Center for Immigration Studies, created a map using the zip code data, showing criminal aliens being released into cities across the country.

The ICE response explained the release of the 169 criminal aliens this way: “Of the 169 ICE detainees with a homicide-related conviction who were released from ICE custody in FY 2013, 131 have been issued a final order of removal. Of the remaining 38 aliens who have not been issued a final order of removal, one was granted voluntary departure by an immigration judge and subsequently departed within the permitted timeframe. Further, 154 of the 169 were released pursuant to court order due to Zadvydas.”

“Zadvydas” refers to the 2001 U.S. Supreme Court decision in Zadvydas v. Davis, which has been interpreted to mean that an immigrant who has not been accepted for reentry into another country after six months can be released.

“We’ve introduced legislation that would reverse the court case that the Obama administration is relying on to excuse its irresponsible release of thousands of criminally convicted aliens,” Grassley said in the press release.

The Zadvydas decision has resulted in what is frequently described as the practice of “catch and release” in immigration law enforcement.