In the case of Nowakowski v. Maroney, Correctional Superintendent in 1966, the petitioner, Nowakowski was convicted for murder and sentenced to life imprisonment by a Pennsylvania court. He appealed his conviction on grounds that he had been denied effective assistance of counsel during his trial as guaranteed under the Sixth Amendment. The Supreme Court held that an accused person is entitled to reasonably competent and effective representation by an attorney acting as their diligent advocate. However, it also stated that not every mistake made by a lawyer would constitute ineffective assistance of counsel unless it affected the fairness of the trial or undermined confidence in its outcome. In this case, despite some errors made by defense counsel during cross-examination and closing argument which were deemed regrettable but not constitutionally fatal; there was no evidence showing these mistakes prejudiced Nowakowski's defense or resulted in an unfair trial. Therefore, his claim for ineffective assistance was rejected.

In the case of Nowakowski v. Maroney, Correctional Superintendent (1966), there was no recorded dissenting opinion from any justice in the Supreme Court. The court denied certiorari, effectively upholding the decision of the lower courts without providing a written explanation or detailed reasoning for their decision. Therefore, it is not possible to summarize a dissenting opinion for this particular case as none exists on record.