Here's a breakdown:
When you DO need a comma before "in that":
* After an introductory phrase:
* Example: "After careful consideration, in that particular case, we decided to move forward."
* After a dependent clause:
* Example: "Since we were already late, in that we missed the train, we decided to call a taxi."
* When separating items in a list:
* Example: "The things I need to pack are my passport, my wallet, in that order, and my phone."
When you DON'T need a comma before "in that":
* When "in that" is part of a prepositional phrase:
* Example: "He was confident in that decision."
* When "in that" introduces a restrictive clause:
* Example: "The person in that suit is the CEO." (The clause is necessary to identify which person)
It's important to note:
* "In that" is often used in formal writing, so it's good to be mindful of your audience and context.
* Sometimes, using a comma before "in that" might be grammatically correct but stylistically awkward. Consider rephrasing the sentence if it sounds clunky.
If you're unsure, it's always best to consult a style guide or a grammar resource.