Why are you suggesting there should be a reverse onus of proof in criminal matters?
The police should prove their case, not the other way around. Plus the OP has a plausible explanation. And let's face it, police have been known to plant evidence when it suits them. (ie Roger Rogerson).
You can see what happens when reverse onus of proof is used in family law. Imagine your wife complains you pushed her one day, she goes to cops, they take out a IVO and you are out of the family home that you bought for 1 to 2 years.
So, how do you go about proving you never pushed your wife?? Proving a negative is extremely difficult to manage and should not be part of a criminal justice system.
And she still doesn't like you it gets extended when she makes up a story that is not true.
I say nooooooo to reverse of proof in criminal matters.