Dominic Mauro, writing on his fantastic site, Barely Legally:
Hey, so, remember that guy Farook and his phone that the FBI really really wants to unlock and poke around in? Sure is funny how the FBI was hilariously inept in their investigation, and now the only way they can get into the phone is by having Apple build a tool to circumvent its own security measures, right?
After all, if you were the FBI, and you wanted a test case, this whole “real live radicalized Muslim terrorist committing an act of war on American soil with pipe bombs and assault rifles before dying in a glorious shootout with the police” thing would be, like, the perfect test case. It sure would be a shame if the traditional investigation went awry, and the only way to get access to the phone was filing a completely novel test case.
If you're not following Mauro's work, you really owe it to yourself to make it a regular read. Not only is the writing good, it's coming from someone who is knowledgable about the justice system. He provides a unique perspective that few of us have the benefit of experiencing professionally.
In this instance, he provides an excellent, concise history about some high(er)-profile test cases that helps provide some insight as to why the FBI is pushing the San Bernadino case so hard.
The FBI clearly wants more access to these devices. Encryption makes their jobs significantly more difficult (if not impossible). Their best bet to gain the support of the courts and the public is to leverage a case that targets the very core of a nation's collective fear. Few things elicit a more violently emotional (and completely irrational) sentiment than the word "terrorism" coupled with the word "Muslim." Regardless of the validity of the government's claims–which, at this point, are beginning to sound much closer to the plot of a shitty 90s cyber-thriller–they don't have much of choice but to pursue this.
Make no mistake, this is not a case about a single phone, a single incident. It's about expanding the powers of the government, and ensuring that unprohibited access to private information is the norm for investigators when they assert they need it. As we've seen many times in the past (something Mauro demonstrates in his piece regarding the Patriot Act), if we relent in even the slightest way, we'll find our way of life altered irreparably. This can't happen.