Can a district include a part of a county that has no people..

[Greedo punched first]

Technically yes, but realistically you'd have to be literally insane to do it.

Yes. That is the case with CA-48. A small part of Irvine that has no residents is in CA-48. If you look at this map and hover over Irvine in this CA-45 map, a very tiny piece of land in Irvine (where nobody lives) is in CA-48. Even though all of Irvine's residents live in CA-45, not all of Irvine is in CA-45.

[Greedo punched first]

Technically yes, but realistically you'd have to be literally insane to do it.

Yes. That is the case with CA-48. A small part of Irvine that has no residents is in CA-48. If you look at this map and hover over Irvine in this CA-45 map, a very tiny piece of land in Irvine (where nobody lives) is in CA-48. Even though all of Irvine's residents live in CA-45, not all of Irvine is in CA-45.

I suspect that is a mapping error. It would make no sense to include unpopulated land in Irvine in another CD that is not needed to make a CD contiguous. I happen to know the guy on the commission that drew CA-48 (the rest of the commission deferred to him on this one, to throw the otherwise disgruntled chap a bone), so I may draw this to his attention. This came up, because I told him I like the design of CA-48 (my CD at the time), and he proceeded to claim credit for it.

Another map of CA-48 also shows the end of the street Canyon Retreat in Irvine inside CA-48. The map doesn't make sense, but it still seems to be the case.