The Evidence: Materials
The fact that there are multiple flaws in the marble used for the kouros suggest that it cannot be an ancient piece. There is a large flaw in the center of the forehead which cannot be a result of damage, as the sculptor clearly attempted to rework one of the statue's curls to hide it. This is not the only flaw in the marble. According to Vassilis Lambrinoudakis, ""the sculptor deliberately used a defective material, trying to conceal some imperfections but tolerating others. This is not the normal attitude of the Archaic sculptor." This stone would never have been used by an archaic artist if it was flawed. There are countless examples of kouroi being abandoned because such a flaw was discovered, such as the unfinished Melanes kouros left on Naxos. This means that either the Getty kouros had an anomalous sculptor who worked around flaws in the stone and is therefore unique in the sample of surviving kouroi, or that the statue is a modern forgery carved by a sculptor who was unaware of archaic attitudes towards imperfections in marble. The latter seems more likely.
 Vassilis Lambrinoudakis, "Some Observations on the Authenticity of the Getty Kouros," In The Getty Kouros Colloquium Athens 25-27 May, 1992 (Athens: Kapon Editions-Greece, 1993), 31.
 Lapatin, "Proof?: The Case of the Getty Kouros," 47.