What is “systemic racism”?

I hear this term a lot but I’m struggling to find a clear understanding of what it is and how far (if at all) that it diverges from racism.

I’ll use variations on a scenario to try and see what you think.

Which of the below in your opinion would be examples of “systemic racism”?

1. Law itself is not racist, the letter of the law is applied with no bias by everyone in the decision-making process, only the circumstances of cases are used to make decisions but a disproportionate number of black people are imprisoned from the process regardless.

2. The law itself is racist against black people which leads to a disproportionate number of black people ending up in prison.

3. The law itself is not racist but it leaves room for racist decisions which lead to a disproportionate number of black people ending up in prison.

I use the definition of racism as:

“prejudice, discrimination, or antagonism by an individual, community, or institution against a person or people on the basis of their membership of a particular racial or ethnic group, typically one that is a minority or marginalized.”

Effectively a decision/action needs to be made on the basis of race for it to be racist (decisions made which affect a race disproportionately but are not made on the basis of race are not racist).

Let me know if any of the above examples sum it up or if you can explain it in a better way.

Also if number 1 is an example of systemic racism should anything be done within that system to change outcomes?

If you think number 3 is, it would be great to hear ideas on how to stop racist decisions being made when deciding on guilt and the length/form of sentences.