Saying that "science is ever changing, and that also applies to law" is exactly the kind of thing that you come up with when you try desperately to link your A-level choices to your chosen subject. Going on to say something about how the law has changed just illustrates how the link to science was completely irrelevant. Being original is all very well, but it needs to be originality about you and your interests, not an original way of linking unrelated A-levels to your subject, which is in danger of just coming across as silly and artificial.
The bottom line is that admissions tutors will not read your application and think, 'Hmmm, science A-levels but applying for law... I need to see some link between these in the personal statement to convince me that this candidate is serious.' What they need to see is evidence of your interest and reading and/or involvement in law.