A legal system, any of them, ought to lay down the principles and the rules that may govern in same manner all possible occurrencies of like circumstances.
Interpreting the laws and rules dictated by the legal system, though, may prove a quite subjective exercise, any intellectual effort being conditional upon the individual experiences made by the acting entity.
Whereas the process of interpreting the law to apply it in a specific circumstance (a process that is often disciplined by the law itself) coincides with the declination of a written, static rule towards the pragmatic, dynamic world of real life, thus recurring to the social feelings about the underlying facts and implied consequences, kind of guidance is (should be) required in that process so as to avoid temerary deviations from the overall sense of the legal system.
Being the yardsticks of such guidance is exactely the role of both the general principles of a legal system and of the case law elaborated by courts in the application of those same rules
The American judiciary is designed to be impartial; the principle of rule of law and idea of blind justice is reiterate the notion. However, the criminal justice system, specifically courts, provide both judges and attorneys discretion which allows for subjectivity to seep into the legal system. For instance, when a person is charged with a crime and law enforcement presents its case to the prosecuting attorney, the prosecutor ultimately makes the decision to or not to prosecute based on his/her subjective opinion on how likely the evidence will prove guilt beyond a reasonable doubt.
The subjectivity is becomes more evident when you consider sentencing disparities among racial demographics. Sentencing disparities highlight how judges subjectively impose criminal sentences, although sentencing guideline exist to prevent cruel and unusual punishments, they do not prevent judges from incorporating their subjective thoughts into sentences imposed. A prime illustration is highlighted in Sarasota Herald-Tribune’s award-winning 2016 "Bias on the Bench" series. One example in the series was Judge Sherwood Bauer who sentenced Chase Legleitner, a white defendant to 2 years in jail and Lamar Lloyd, a black defendant to 26 years after both pleaded no contest to two counts of armed robbery in separate cases in Florida; the subjectivity was obvious because both defendants had one prior misdemeanor and had the same number of points on a scoresheet used to determine sentencing.
The legal system can acquire the status of subjectivity based on its application by persons charged with implementing the law, especially judges in courts, whether judges of administrative courts or ordinary judicial courts.
After reading the interesting comments of both Jacobi Grant and مسعود كشحه I esteem to be necessary to clarify that the subjectivity of the legal system should be kept separate and distinct form the subjectivity of its "usage", or application, by the persons and organs who are called to implement them.
In such respect, no field of human activity may be deemed to be "objective", as the human interference with the system, any system in whatever domain, is by essence, ontologically subjective.
It would be the same even if the human role were to be replaced by some sort of AI, in effect: software is programmed by humans, who also dictate what are the reference databases to be utilized for benchamarking the Y/N decision
There is no absolute subjectivity for any legal system because it must be affected by other legal systems close to it. Legal systems must also be affected by international influences and global politics surrounding it in light of a new world that is a small village.