A recent article on Vox media explains that a criminal defense lawyer has not been part of the United States Supreme Court in over 25 years. This is problematic, since many of the cases are ones that concern criminal cases, yet there is no one on the bench to discuss represent those who provide a defense in those cases.
The court has two ex-prosecutors currently, and if President Trump gets his appointment of Neil Gorsuch confirmed, the court will have a total of three, making up 1/3 of the justices.
The Vox article explains that:
Appellate defense lawyer Timothy O'Toole points out that the Court has veterans of both sides of civil cases (defendants' and plaintiffs' lawyers) and one side of criminal cases (prosecutors). "But the one group that seems kind of outside that box, particularly on the Supreme Court, are defense lawyers. And that's a shame."
Defense lawyers and scholars worry this isn't an accident; it's the result of the structure that shapes who can get nominated to the Supreme Court to begin with. Federal judges tend to be people who "ticked all the political checkboxes on their career starting from when they were 15," says Tejas Bhatt, assistant public defender for New Haven, Connecticut. Often one of those boxes is working as a prosecutor.
Even beyond any particular career experience, the system rewards "people who don't take controversial positions, they don't do controversial things, who don't issue controversial opinions, who do seem to hew more toward law and order and enforcement."