I'm trying to understand a particular use of the word doch
If somebody says es ist meine Schuld, meaning "it's my fault", may I use doch in response to convey, essentially, "no, on the contrary, it's not your fault"?
Let me try to give you an idea on how to use "doch" in that particular context with a short story:
You can see that depending on context doch is used in different meanings that can not be translated 1:1. It gets further comlicated because the meanig of a sentence may change with emphasis (see 4., 6., 8.). Example 11. may come close to what you asked.
"Es ist meine Schuld" is a complete sentence, means It's my fault
it's not your fault would be:
If you see somebody is punished for something you did, you may say (directing the sentence to the punisher):
Or you could use it to console somebody (Don't worry, it's my fault). But it needs the statement, somebody else is taken the blame or feels responsible for your fault.
No, this is not possible. Doch can only be used as a response to negative statements. For example, if someone says
then you can answer
to express that you think it is their fault (although they deny). I believe there's no short translation for this doch to English.
If someone says
then it doesn't make sense to simply answer with Doch, but you could very well say