Focusing on solving a murder and being willing to scarifies the privacy of everyone, even the people that are in no real danger is foolish. The billions of dollars spend on spying on regular people are mostly wasted. Taking the same money and directing them towards prevention may yield better results. I'm not talking about the kind of prevention where the FBI pick up some terrorist just before he's about to bomb something. I'm talking about the kind where we avoid that people become terrorists.
If companies and individuals make it impossible for the governments to spy on people infeasible we might get more focus on prevention.
Also, strip away the privacy of the murderer and you strip away the privacy for all of us, including those who fight oppressive regimes and dictatorships. That might not be a sensible tradeoff.