It has become increasingly evident that the Justice Department violated the constitutional rights of Boston bombing suspect Dzhokhar Tsarnaev. He apparently was questioned for hours without being given his Miranda warnings, and the interrogation continued even after he explicitly requested an attorney. It is disturbing that the Justice Department would risk its criminal prosecution by ignoring such basic rules and even more disturbing for what this says as to its view of the Constitution.

There is much that we still do not know about how Tsarnaev was treated by federal law enforcement after his arrest. Boston Police Commissioner Edward Davis described extensive questioning of Tsarnaev in the hospital, the first time on "Saturday evening into Sunday morning" and the second on "Sunday evening into Monday morning." All of this was before Tsarnaev was arraigned by a federal magistrate judge on Monday morning, April 22. According to an Associated Press report, the questioning lasted a total of 16 hours before Tsarnaev stopped cooperating upon being informed of his right to remain silent. A senior congressional aide said Tsarnaev had asked several times for a lawyer, but that request was ignored.

The law is clear that when a suspect is taken into custody, he or she must be given Miranda warnings, and all questioning must cease when the suspect requests a lawyer. Any statements gained in violation of these requirements must be suppressed and cannot be introduced as evidence. It may turn out, of course, that Tsarnaev will plead guilty or that he can be convicted at trial without these statements. But why would the Justice Department want to risk that?

Attorney General Eric Holder Jr. said on the Sunday morning talk shows three years ago, and others have said since, that terrorism suspects such as Tsarnaev do not need to be given Miranda warnings because of an emergency exception. But that exception allows questioning to deal with an imminent threat to public safety; it would justify initial questioning to be sure that there were no other bombs, not 16 hours of questioning.

THE PUBLIC-SAFETY EXCEPTION

The emergency exception to Miranda v. Arizona, which Holder relied on, was announced by the U.S. Supreme Court in New York v . Quarles in 1984. A woman told the police that she had been raped by a man with a gun. When the police caught the suspect in a grocery store, they saw an empty holster and no gun. The man was asked about the location of the gun, and he told the officer where to find it in some nearby boxes. The Supreme Court ruled that, although the suspect had not yet been given Miranda warnings, the statement about the gun was admissible against him because of the urgent need to find the weapon.

In other words, the public-safety exception applies only when police are acting in an emergency to prevent serious immediate harm. If the police needed to question Tsarnaev as to the location of other bombs, the emergency exception would apply. But Holder has said that no such threat existed. It appears then that the questioning of Tsarnaev without reading him his rights violated the Fifth Amendment. That could well mean that any incriminating statement he made will need to be excluded from use as evidence.

But even if the emergency exception somehow applied to allow questioning of Tsarnaev before he was given his Miranda rights, that does not justify continued questioning after he requested a lawyer. The Supreme Court never has recognized a public-safety exception to the constitutional requirement for providing an attorney to a suspect who requests one.

The apparent authority for the Justice Department’s action is a memorandum on the public-safety exception from Holder dated October 21, 2010. The memo states: "There may be exceptional cases in which, although all relevant public safety questions have been asked, agents nonetheless conclude that continued unwarned interrogation is necessary to collect valuable and timely intelligence not related to any immediate threat, and that the government’s interest in obtaining this intelligence outweighs the disadvantages of proceeding with unwarned interrogation."

In other words, the Justice Depart­ment memo says that the public-safety exception can be invoked even when there is no immediate threat to public safety. No Supreme Court decision supports this. Any time the Justice Department does this it risks exclusion of any evidence it gains.

Most troubling is the underlying premise that the Constitution applies differently in cases of terrorism. At the very least, such an approach would be problematic because of the inability to define what is terrorism. If the Boston bombings were a terrorist act, then weren’t the anarchist bombings of the early 20th century or the bombing of the federal building in Oklahoma City by Timothy McVeigh and Terry Nichols also terrorist acts?

More importantly, the assumption is that the government cannot successfully investigate, prosecute and convict if it has to comply with the Constitution. This was the assumption underlying the calls by senators Lindsey Graham (R-S.C.) and John McCain (R-Ariz.) to have Tsarnaev held as an enemy combatant and prosecuted in a military tribunal. The Obama administration thankfully rejected that suggestion, hopefully recognizing that federal courts repeatedly have shown that they can handle terrorist prosecutions and that convictions can be obtained with proceedings that are in full compliance with the Constitution.

There is an enormous temptation to suspend the Constitution in a crisis. But the Constitution is not a luxury to be indulged until the ends justify other means. The Fourth, Fifth and Sixth Amendment rights of all criminal defendants must be obeyed, no matter how heinous the crime and regardless of whether it is labeled an act of terrorism. The Bush administration repeatedly forgot this, and it is a shame that in treating Tsarnaev the Obama administration did, too.

Erwin Chemerinsky is dean and distinguished professor of law at the University of California, Irvine School of Law.