Presumptions

Courts make certain assumptions (presumptions) when interpreting an Act unless the Act clearly states the opposite (rebuts the presumption)
The presumption in criminal law is that the prosecution has to prove its case beyond reasonable doubt but that presumption is rebutted for diminished responsibility and insanity where the burden of proof is on the defence

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Presumption Against a Change in the Common Law

Assumed that the existing case law (common law-made by Judges) will still apply unless the Act to be interpreted says the opposite
Leach v R (1912)-CL stated that a wife could not be forced to give evidence against her husband. the Criminal Evidence Act 1898 didn't state that this presumption had been rebutted so still applied

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The CL rule is that no-one should be convicted of an offence unless it is proved that they had the intention to commit it
Sweet v Parsley (1970) charged with being concerned with the managment of premises that were being used for the purpose of smoking cannabis-was mens rea required? The Act didn't say anything about Mens Rea
- D was a teacher and rented out a farmhouse to some students and they were frowing and smoking cannabis. D didn't know this.
- The Act refered to somebody who managed the premises and said nothing about their state of mind or intention.
- D convited and lost her job.
- Appeal to HoL. They held there was a presumption that a guilty state of mind (mens rea) was required.
- The Act had not rebutted that and D was acquitted.

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The Crown (State) is not bound by any statute unless the Act expressly says so
Legislation doesn't apply retrospectively-will not apply to anthing that happened before the Act was passed unless the Act makes it clear that it can be applied retrospectively

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