Tim Cook. AP As expected, the US Department of Justice filed a legal response on Thursday to Apple's refusal to help the FBI unlock an iPhone used by one of the San Bernardino shooters.

An hour after the DOJ brief was filed, Apple general counsel Bruce Sewell delivered a tense and angry response in a conference call with reporters.

He called the DOJ response a "cheap shot" and said that its tone "reads like an indictment."

"In 30 years of practice I don't think I've ever seen a legal brief more intended to smear the other side," Sewell said.

While his comment isn't an official legal response, it certainly underscores that the battle between the two sides has become more heated and emotional as the debate drags on.

An Apple attorney actually advised that the company thought the battle was getting less heated after Sewell and FBI Director James Comey testified before Congress earlier this month, but was disappointed when they saw the official DOJ legal response.

Of course, the DOJ brief had some severe language, too, calling Apple's rhetoric "false" and "corrosive":

Apple's rhetoric is not only false, but also corrosive of the very institutions that are best able to safeguard our liberty and our rights: the courts, the Fourth Amendment, longstanding precedent and venerable laws, and the democratically elected branches of government.

On March 22, Apple and the FBI will meet at a hearing in federal court in Riverside, California.

Here's Sewell's full statement:

First, the tone of the brief reads like an indictment. We've all heard Director Comey and Attorney General Lynch thank Apple for its consistent help in working with law enforcement. Director Comey's own statement that "there are no demons here." Well, you certainly wouldn't conclude it from this brief. In 30 years of practice I don't think I've seen a legal brief that was more intended to smear the other side with false accusations and innuendo, and less intended to focus on the real merits of the case.

For the first time we see an allegation that Apple has deliberately made changes to block law enforcement requests for access. This should be deeply offensive to everyone that reads it. An unsupported, unsubstantiated effort to vilify Apple rather than confront the issues in the case.

Or the ridiculous section on China where an AUSA, an officer of the court, uses unidentified Internet sources to raise the spectre that Apple has a different and sinister relationship with China. Of course that is not true, and the speculation is based on no substance at all.

To do this in a brief before a magistrate judge just shows the desperation that the Department of Justice now feels. We would never respond in kind, but imagine Apple asking a court if the FBI could be trusted "because there is this real question about whether J. Edgar Hoover ordered the assassination of Kennedy — see ConspiracyTheory.com as our supporting evidence."

We add security features to protect our customers from hackers and criminals. And the FBI should be supporting us in this because it keeps everyone safe. To suggest otherwise is demeaning. It cheapens the debate and it tries to mask the real and serious issues. I can only conclude that the DoJ is so desperate at this point that it has thrown all decorum to the winds....

We know there are great people in the DoJ and the FBI. We work shoulder to shoulder with them all the time. That's why this cheap shot brief surprises us so much. We help when we're asked to. We're honest about what we can and cannot do. Let's at least treat one another with respect and get this case before the American people in a responsible way. We are going before court to exercise our legal rights. Everyone should beware because it seems like disagreeing with the Department of Justice means you must be evil and anti-American. Nothing could be further from the truth.