on the case
(informal) Actively working on something.
Synonym: on it
It's possible this whole "Why do Latinos love Morrisey?" question will haunt us forever. Fortunately, Canadian academics are on the case. Chuck Klosterman
My role in it was not as central as it was in some of the later cases considering I was younger then and I was playing a role of co-counsel on the case. Floyd Abrams
I don't know of any case that involves computer hacking where there were multiple defendants charged where there wasn't an informant on the case. Kevin Mitnick