What is the origin of the idiom "on the case" and when to use it?

The idiom "on the case" has its origins in detective or police jargon, where investigators are said to be "on the case" when they are actively working on solving a particular crime or mystery. It conveys the idea of someone being actively engaged in addressing a specific task, situation, or problem, often with a sense of dedication, determination, or expertise. Over time, the phrase has evolved to be used in various contexts beyond law enforcement, indicating someone's commitment to tackling a particular issue or being responsible for a specific matter.