isWitnessSetMember(...,Verbose=>Boolean)
Use Verbose=>true for additional output, which includes the input and solution file names used by phc.
i1 : R = CC[x11,x22,x21,x12,x23,x13];
i2 : system = {x11*x22-x21*x12,x12*x23-x22*x13};
i3 : V = numericalIrreducibleDecomposition (system); found 4 irreducible factors
i4 : W = first V#4;
i5 : isWitnessSetMember(W, point{{0,0,0,0,0,0}}) o5 = true