One who, not being present, contributes as an assistant or instigator to the commission of an offense. [
1913 Webster]
" This word, as used in law, is spelt accessory by Blackstone and many others; but in this sense is spelt accessary by Bouvier, Burrill, Burns, Whishaw, Dane, and the Penny Cyclopedia; while in other senses it is spelt accessory. In recent text-books on criminal law the distinction is not preserved, the spelling being either accessary or accessory."
[1913 Webster]