Sie and sie

[Giomach]

I've come across some interesting cases in a book translated from English.

wenn ich an diejenigen denke, die Sie verfolgen

The English was "when I think of those you persecute", but am I right in thinking the German could equally well mean "when I think of those who persecute you"?

Elsewhere in the same book, I'm fairly sure the translater got it wrong.  He wrote:

Wissen Sie, ob sie tot oder lebendig sind?

The English was "do they know whether you are dead or alive?"

I wonder how such ambiguities are avoided in critical situations, eg. air traffic control, or on the battlefield.