A method of fabricating a guard structure can include depositing an insulating material over at least a portion of electrical signal conductors disposed on a component of a probe card assembly, and depositing an electrically conductive material onto the insulating material and at least a portion of electrical guard conductors disposed on the component of the probe card assembly. Each signal conductor can be disposed between a pair of the guard conductors. The probe card assembly can include a plurality of probes disposed to contact an electronic device to be tested. The signal conductors can be part of electrical paths within the probe card assembly to the probes.