Knives that pose the most serious threat to body armour systems are termed “engineered”. This in Plain English means a blade type that when “fully impacted” into a wooden block, would retain its shape and pointed effectiveness to be capable of being used again in its original, relatively undamaged state.
If you were to examine most kitchen knives, you might determine that such “drawer knives” do not really qualify for inclusion. Fully impacting a bread knife into a wooden surface would probably snap the blade. In fact, most household knifes will bend if presented with any degree of force. The instant a Knife starts to bend is the physical energy point where the pointed knife weapon looses its penetration potential.
In contrast to the above, knives purchased from specialist shops are quite different - they are made of high grade steel and drop into the “engineered” category. They are capable of retaining their shape at maximum human impact energy. Such blade types are what body armour systems must resist to qualify for certification. The newest test blade in the UK 2007 Police standard is just such a blade - with a pin sharp tip, and virtually “no give” in its construction.
The Spike Test is considerably more severe than the knife test. Materials capable of preventing knives penetrating will often completely fail to stop pointed weapons of relatively small diameter.