When and where is the accused OFFICIALLY expected to prove his innocence? In a 'she said - he said' situation, when and where is the accuser in advantage?

Is it written in the law, or is it just how the system operates?

In a criminal law?

In a college court?

In a labour law?

In various countries?

I am looking for resources, please refrain from posting anecdotal evidence. Thank you.

Example:

Type of resource: Survey of existing practices.

Domain: Title IX college courts in the US.

https://www.saveservices.org/2020/02/survey-confirms-unfairness-of-campus-title-ix-on-due-process/