I've seen Blade Runner many times but I'm currently reading Do Androids Dream of Electric Sheep? for the first time and I find myself wondering something I've never considered before: Why does Deckard need to use the Voight-Kampff test on the remaining escaped androids?
I know he needs to use the test to figure out who is an android and who isn't, but in this case Deckard is given his targets beforehand. And certainly, when an android is asked to take an empathy test, they would know their time is up - it necessarily robs the tester of the element of surprise.
In Chapter 9, Deckard goes to the opera house after Luba Luft.
He reexamined the poop sheet, then leaned back, satisfied. I've now seen my third Nexus-6 android, he realized. This is Luba Luft.
Here, Deckard has the obvious advantage. Luft is unaware that she is being hunted at all. Given he knows that she is an android already, why doesn't he proceed with the next part and
kill retire her right away so he can collect the bounty? Why bother with the test?