presex flower reliability rate

So my friend has some plants in veg... 3 show pistils as presex flowers 1 shows what looks like female part without pistil and the rest show little 'claw' looking things that are more ball-shaped.

what is the reliability of pre-sex indicators? should he slay all the plants which appear to be male or will they show 'true' sex @ 12/12 time?

They will true "true" sex at flower time. I wouldn't kill anything until I'm sure. Great news on the pistils though! Happy growing my friend. Definitely sounds like you got some males in there somewhere though.

Damn. Well at least he has some for sure!