The best way can explain the criminal justice system is analogous to chess. The District Attorney makes the first move by filing a complaint and the defense then responds to that move. All moves are done in the open as CA statutes and Brady require. The moves are honest and out in the open with no hidden agenda or other considerations than what is on the board.
In an ideal system two things would be true. First, white would always win because only cases a prosecutor believed they could prove beyond a reasonable doubt would be filed. Second, all cases would be decided solely on the facts and the relevant law.
But, the reality is that our criminal justice system is not black and white. Prosecutors have policy considerations that may limit their discretion in filing complaints or making offers. Defense attorneys, especially the Public Defender, have large case loads that require time and extraordinary effort to litigate. But despite these logistical or policy issues the primary concern is the client. In the case of the prosecutor its the victims of crime and society; for the defense its the criminal defendant.
Clients may not be willing to undergo the drudgery of the system. A client may not be able to afford a trial along with its many expenses or they have other concerns like immigration status or family law issues that make them unwilling to participate.
The criminal justice system despite its many problems is improving because society is realizing its importance spreads beyond the courtroom. There are documentary films like Netflix “13th”, “Gideon’s Army”, “The Smartest Guys in the Room”, etc., that highlight the difficulties and issues plaguing the system.
A healthy system requires advocates on both sides willing to act honestly while vigorously defending their positions and clients/victims willing to engage. Those twin goals happen through education and civics.
We are the land of the free and the home of the brave. We need to start acting like it starting with ourselves. We all want the same thing and by community engagement we can balance interests and further a system that protects the most vulnerable while at the same time not stepping on our Constitutional values.