What is a key characteristic of laws in the UK justice system according to legal principles?

The key characteristic of laws in the UK justice system that underscores their reliability and fairness is that they cannot be retrospective. This principle means that new laws are not applicable to actions that were committed before the law was enacted. This characteristic helps ensure that individuals are only held accountable under laws that were in place at the time of their actions, thus upholding the legal concept of fairness and protecting citizens from arbitrary punishment.

In the context of the options provided, this principle reinforces the importance of predictability in the legal system, allowing individuals to understand what is lawful and what is not during a given timeframe. This contrasts with the idea of laws changing at any time, which could create confusion and instability in the legal framework, or the notion that laws are subjective, which could lead to arbitrary enforcement. It also distinguishes the justice system from merely focusing on serious offenses, as laws apply to a wide range of behaviors and ensure that all individuals are treated consistently under the same legal standards.