I was studying parts of speech and while learning common noun I found a special category that my book refer as plural common noun and there is written The + Adjective gives a plural common noun but there are exceptions. It is written that The deceased and The accused are two exceptions that are not plural common noun instead they work as singular noun.
I did a quick google search but couldn't find anything relevant except this. Looking at the examples in my link I could decide whether these two are common noun (but not plural common noun).
My question- is The deceased or The accused a common noun?