What is the standard of conduct of a defense attorney in a criminal proceeding?

As noted by the defense, an attorney for a defendant in a criminal action or proceeding is required to competently and diligently represent his or her client (see NYS Code of Professional Responsibility, Rules 1.1, 1.3). Competent and diligent representation requires defense counsel to conduct a thorough investigation and failure to do so may result in a finding that a defendant was not afforded meaningful representation. As stated in People v. Oliveras (21 NY3d 339, 347 [2013]):