In the NOTECH BEH Marker system, under what circumstance can both Capt and FO fail their CRM?.

If there is a technical sequence is recorded, eg EGPWS trigger, can only the CAPT fail his CRM as he is the commander and therefore responsible?

I guess when you refer to "failing CRM", you are referring to a line check. Under normal NOTECH guidelines, you would not fail the line check unless there are technical consequences. It may, however, be noted that there are unacceptable non-technical skills, and the consequences of this will be down to the individual company/organization procedures.
Whether the non-technical skills failures are down to the captain or the copilot (or both) will be for the trainer/examiner to determine.

What on earth is a NOTECH BEH Marker system?

PM

Captain at my former airline failed an LPC/OPC because of poor CRM despite achieveing the desired outcome of the sim detail.

A behavioual marker system is a way of assessing non-technical skills in the cockpit.

Spandex- I guess its up to each individual airline what their pass and fail criteria are for an OPC.