I have the following JSON data:
{\"id\":\"111\",\"case\":\"Y\",\"custom\":{\"speech invoked\":\"no\",\"input method\":\"hard\",\"session ID\":\"420\"}}
Building upon Joe Harris' answer, you can use the @csv filter so that strings are properly quoted and escaped when necessary :
jq -r '[.case, .custom."speech invoked", .custom."input method"] | @csv'