I am not sure why confession of an accomplice is not enough. Plenty of people have been convicted on that.
Additionally, I don't believe NY State Law permits that, but someone with legal expertise might step in to clarify as I am unsure:
<snip, BBM>
S 60.22 Rules of evidence; corroboration of accomplice testimony.
1. A defendant may not be convicted of any offense upon the testimony
of an accomplice unsupported by corroborative evidence tending to
connect the defendant with the commission of such offense.
2. An "accomplice" means a witness in a criminal action who,
according to evidence adduced in such action, may reasonably be
considered to have participated in:
(a) The offense charged; or
(b) An offense based upon the same or some of the same facts or
conduct which constitute the offense charged.
3. A witness who is an accomplice as defined in subdivision two is no
less such because a prosecution or conviction of himself would be barred
or precluded by some defense or exemption, such as infancy, immunity or
previous prosecution, amounting to a collateral impediment to such a
prosecution or conviction, not affecting the conclusion that such
witness engaged in the conduct constituting the offense with the mental
state required for the commission thereof.
Article 60 | NYS Criminal Procedure Law | Rules of Evidence