evidentiality in English

English has no evidential paradigm. No affix, particle or auxiliary marks a proposition as seen, inferred, reported or assumed, and a speaker who needs the source of information stated does so with a verb such as saw or heard, or with an adverb such as apparently, reportedly or evidently. Those adverbs are lexical items that can be omitted, stacked and questioned, none of which is true of a grammatical marker.

Two candidates might have qualified and do not. The modal must carries an inferential reading, so the perfect under it reports a conclusion drawn from evidence rather than a direct observation. That reading is one use of a word whose other uses express obligation outright, it is never required in any context, and it contrasts with no closed set of alternative information sources. It is a modal that happens to permit an inferential interpretation, and modality is a different question filed under mood.

The second candidate is the reportative use of a verb of speaking in an impersonal frame. It is a clause, not a marking, and it takes a whole complement of its own. Nothing here forms a paradigm: there is no obligatory slot in which one of a closed set of markers must appear stating how the speaker knows, which is what a system of this kind consists in. The absence recorded here is an assertion about the language and not a gap in the description of it.