In Season 1 Episode 10 Nelson asks "have you killed anyone before?". Matt said no.
But Matt actually killed Nobu!
Why is he lying?
Nelson asks "did you killed anyone before?"
The conversation goes something like.
Foggy Are you telling me the truth?
Matt I didn't kill him, Foggy. (referring to the murdered junkie)
Foggy So, you've never, you've never gone that far?
Matt No. But I.. I wanted to after Elena after everything Fisk had done. I... I went to a warehouse I thought he'd be at. I went to kill him.
Foggy: It's not enough playing judge and jury? You gotta add executioner to the list?
So Foggy isn't actually asking if he's "killed before" but rather has he murdered someone while he's acting like a vigilante.
Nobu "dies", sure, but it was an act of self-defence not murder or an execution.
The emphasis isn't on "never"...it's on "that far". As far as murder.
It's a fine distinction, perhaps, but still the truth.