Jeanne Marie Neumann, in Lingua Latina: A College Companion, suggests
You will sometimes find quis (i.e. the form of the interrogative pronoun) used instead of quī (the form of the interrogative adjective) before a noun in questions of identity: Quis servus? Medus. [emphasis mine]
In a previous answer, @fvogel offered these examples, all of which meet the conditions Neumann imposes:
From Horace Satires:
Quis homo hic est? (I.6)
From Plautus Miles Gloriosus:
Quis homo id vidit? (176)
Quis homo in terra te alter est audacior? (313)
Quis homo sit magis meus quam tu es? (615)
I find another set of examples in Cicero, In Catilinam II:
O fortunatam rem publicam, si quidem hanc sentinam urbis eiecerit! Uno mehercule Catilina exhausto levata mihi et recreata res publica videtur. Quid enim mali aut sceleris fingi aut cogitari potest, quod non ille conceperit? quis tota Italia veneficus, quis gladiator, quis latro, quis sicarius, quis parricida, quis testamentorum subiector, quis circumscriptor, quis ganeo, quis nepos, quis adulter, quae mulier infamis, quis corruptor iuventutis, quis corruptus, quis perditus inveniri potest, qui se cum Catilina non familiarissime vixisse fateatur? quae caedes per hosce annos sine illo facta est, quod nefarium stuprum non per illum?
In A Preparatory Course in Latin Prose Authors, Albert Harkness writes of this paragraph,
Quis, though more commonly used substantively, may be used adjectivally, when, as in this case, the inquiry relates, not to the character of the person or thing, but to the person or thing itself. Thus quis veneficus is not what kind of poisoner, but what poisoner, i.e., which one.
It's interesting, though, that Cicero uses quis here only for masculine nouns, but for mulier infamis he uses quæ. I wonder whether quis as a noun is used in place of adjectival qui but not adjectival quæ.
