Third-umpire
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Dodgy stuff, too close to call, of [dubious merit], some characteristic or aspect that [the jury is still out] on. Something that is debatable.
Etymology: Akin to when during a cricket match the on field umpires are faced with a decision that is too difficult to make and so they refer to the [Third Umpire] for a ruling.Third-umpire meaning & definition 1 of Third-umpire.