It is the wear pattern that matches a particular shoe print to a particular shoe. However, in order to make that 1-1 match, you need an actual shoe worn by a suspect to compare to the print. The HP oribitals that JY owned went missing, therefore, no way for the analyst to say that JY's shoe made that imprint.
There is no question that JY owned a shoe of the same type that left the print - there is a receipt to prove it. Luckily for him, he ditched those shoes before the police seized his belongings on the night of 11/3/06. Fortunately for the prosecution there were so few size 12 orbitals sold, that the probability that same random killer who was in Raleigh owned a pair just like the victim's husband is prohibitively low.