The probability of brittle fracture is affected, aside from the crack driving force, by changes in constraint, loading rate and crack propagation due to an increase in the sampling volume. In addition, crack propagation, per se, can lead to constraint changes and it also affects the effective strain rate at the crack tip. Especially in the case of leak before break (LBB) where a surface crack transforms instantaneously to a through-wall crack, the increase in local strain rate combined with constraint change and ductile crack extension can be sufficient to cause a transition from ductile fracture to brittle fracture. This, and other similar events, require the development of an advanced Master Curve procedure to account for combined effect of constraint, ductile tearing and loading rate on the brittle fracture probability. A simplified methodology for achieving this is outlined and demonstrated here.