Is there a judgment clarifying difference between 'should have' and 'must have'?

Is there any court judgment that clarifies the difference between 'should have' and 'must have'? For reference, there is a judgment in a similar matter in the case of Rajbeer Singh vs. State of Punjab, where the court stated that 'should have' is directory, whereas 'must have' is mandatory. For reference there is judgment in similar matter in the case of RAJBEER SINGH VS STATE OF PUNJAB ' where court has said that 'should have' is directory whereas 'must have' is mandatory.