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Failing to obtain an expert witness does not automatically constitute ineffective assistance of counsel under Strickland. This article explains how Mackoon v. Nogan addresses deficient performance and prejudice, the role of cross-examination, the value of materially different rebuttal testimony, federal habeas review, and matching an expert to the disputed issue.
Failing to obtain a defense expert does not automatically constitute ineffective assistance of counsel. Under Strickland v. Washington, a defendant generally must establish both constitutionally deficient performance and resulting prejudice.
That issue was central to Mackoon v. Nogan, a 2022 federal habeas case from the District of New Jersey. Mackoon argued that trial counsel should have retained an expert to rebut the State's orthopedic and biomechanical testimony. The district court denied relief, concluding that the New Jersey Appellate Division had not unreasonably applied Strickland in finding no prejudice.
This guide explains how courts evaluate omitted-expert claims, why the substance of the missing testimony matters, and what Mackoon illustrates about Strickland prejudice.
David Mackoon was convicted of offenses arising from three masked, armed jewelry-store robberies in New Jersey, all recorded by surveillance cameras.
At trial, a cooperating witness identified Mackoon from footage of the second robbery and testified that Mackoon had "short arms" but could hold a gun and drive a vehicle.
The State also presented Dr. Zafer Termanini as an expert in orthopedic surgery and biomechanics. After examining Mackoon and reviewing the second robbery footage, he testified that Mackoon had a congenital deformity affecting both arms and limiting hand movement.
Rather than identifying Mackoon through conventional characteristics, Dr. Termanini compared Mackoon's physical limitations with the movements shown in the footage and found them consistent with someone who had Mackoon's condition.
The Supreme Court established the governing framework in Strickland v. Washington, 466 U.S. 668 (1984).
A defendant generally must establish two elements:
Courts apply a strong presumption that counsel's conduct falls within the broad range of reasonable professional assistance and may reject a claim on either element without deciding the other.
In Harrington v. Richter, 562 U.S. 86 (2011), the Supreme Court also rejected a categorical rule requiring defense counsel to retain an expert simply because the prosecution presents one. Depending on the record and counsel's strategy, cross-examination and other trial approaches may be reasonable.
Failing to obtain a defense expert does not automatically constitute ineffective assistance of counsel. Under Strickland v. Washington, a defendant generally must establish both constitutionally deficient performance and resulting prejudice.
That issue was central to Mackoon v. Nogan, a 2022 federal habeas case from the District of New Jersey. Mackoon argued that trial counsel should have retained an expert to rebut the State's orthopedic and biomechanical testimony. The district court denied relief, concluding that the New Jersey Appellate Division had not unreasonably applied Strickland in finding no prejudice.
This guide explains how courts evaluate omitted-expert claims, why the substance of the missing testimony matters, and what Mackoon illustrates about Strickland prejudice.
David Mackoon was convicted of offenses arising from three masked, armed jewelry-store robberies in New Jersey, all recorded by surveillance cameras.
At trial, a cooperating witness identified Mackoon from footage of the second robbery and testified that Mackoon had "short arms" but could hold a gun and drive a vehicle.
The State also presented Dr. Zafer Termanini as an expert in orthopedic surgery and biomechanics. After examining Mackoon and reviewing the second robbery footage, he testified that Mackoon had a congenital deformity affecting both arms and limiting hand movement.
Rather than identifying Mackoon through conventional characteristics, Dr. Termanini compared Mackoon's physical limitations with the movements shown in the footage and found them consistent with someone who had Mackoon's condition.
The Supreme Court established the governing framework in Strickland v. Washington, 466 U.S. 668 (1984).
A defendant generally must establish two elements:
Courts apply a strong presumption that counsel's conduct falls within the broad range of reasonable professional assistance and may reject a claim on either element without deciding the other.
In Harrington v. Richter, 562 U.S. 86 (2011), the Supreme Court also rejected a categorical rule requiring defense counsel to retain an expert simply because the prosecution presents one. Depending on the record and counsel's strategy, cross-examination and other trial approaches may be reasonable.
The procedural posture of Mackoon matters because the federal district court was reviewing a state conviction under 28 U.S.C. § 2254.
When a state court has adjudicated a federal claim on the merits, § 2254(d) sharply limits federal habeas relief. A petitioner must show that the state-court adjudication resulted in a decision that was contrary to, or involved an unreasonable application of, clearly established federal law as determined by the U.S. Supreme Court, or was based on an unreasonable determination of the facts in light of the evidence presented in the state-court proceeding.
The district court concluded that Mackoon had not met that standard.
During post-conviction proceedings, Mackoon presented a letter from forensic pathologist Dr. Mark Taff, who questioned the value of the surveillance footage for medical diagnostic identification. He cited problems including blurriness, black-and-white footage, and the camera angle.
Those criticisms did not directly address Dr. Termanini's central opinion. The State expert focused on whether the person's arm and hand movements were consistent with Mackoon's physical limitations, not on conventional identifying characteristics.
The appellate court therefore concluded that Dr. Taff's proposed testimony would have added little new information directly addressing that opinion.
Trial counsel had already raised several of the same criticisms during cross-examination.
According to the court's opinion, counsel established that Dr. Termanini:
Defense counsel returned to the video quality and other limitations during closing argument.
The post-conviction court described the cross-examination as vigorous. The jury also viewed the surveillance footage and was instructed that it did not have to accept the expert's opinion.
The federal district court focused on whether the New Jersey Appellate Division had unreasonably applied Strickland in rejecting Mackoon's prejudice argument.
The state court concluded that Dr. Taff's proposed testimony did not materially undermine Dr. Termanini's central opinion and that many of the same criticisms had already been developed through cross-examination. It therefore found no reasonable probability of a different verdict.
The federal district court held that this determination was not an unreasonable application of Strickland and denied habeas relief on the claim.
Mackoon does not mean that failure to consult or call an expert can never support an ineffective-assistance claim.
The district court contrasted Mackoon's case with Showers v. Beard, 635 F.3d 625 (3d Cir. 2011). There, a forensic pathologist testified during collateral proceedings that the lethal dose of liquid morphine could not have been administered surreptitiously or forcibly and that Showers's husband likely committed suicide. The Third Circuit affirmed the district court's grant of habeas relief.
Showers also involved appellate counsel's failure to raise trial counsel's omission. The Third Circuit concluded that the underlying trial-counsel claim had merit and that appellate counsel was ineffective for failing to preserve it.
The key difference was what the omitted testimony added. In Mackoon, the proposed expert did not directly rebut the State expert's central opinion. In Showers, the omitted expert challenged a central prosecution theory and supported a materially different explanation of the death. The comparison shows why the substance of the missing testimony matters more than the mere absence of a defense expert.
When specialized testimony becomes important in a criminal case, counsel may need to consider whether another expert would provide genuinely new analysis or mainly repeat points that can be developed through cross-examination.
Relevant considerations may include:
These considerations do not replace the fact-specific Strickland analysis or applicable procedural requirements. They help distinguish potentially significant new evidence from largely cumulative criticism.
Mackoon illustrates the importance of considering whether a proposed rebuttal expert's analysis directly addresses the opinion being challenged. The State expert focused on orthopedic conditions, biomechanics, and observed movement, while the proposed forensic pathologist focused mainly on the video's limitations as an identification tool. Depending on the issue, meaningful rebuttal analysis may require reviewing medical records, imaging, measurements, surveillance footage, and the materials or processing used in the challenged analysis.
The expert's role is to analyze those specialized issues. Whether counsel's performance amounted to ineffective assistance remains a legal determination for the court.
Can failing to hire an expert witness constitute ineffective assistance of counsel?
Yes, in some circumstances. A defendant generally must satisfy both parts of Strickland by showing constitutionally deficient performance and a reasonable probability that, but for counsel's deficient performance, the result of the proceeding would have been different.
Must defense counsel hire an expert whenever the prosecution uses one?
No. The Supreme Court has not imposed a categorical rule requiring a defense expert whenever the prosecution presents expert testimony. Depending on the circumstances, investigation, cross-examination, and other trial strategies may be relevant to whether counsel acted reasonably.
What must a defendant show about an expert who was not called?
The circumstances matter, but identifying an expert who disagrees with the prosecution's expert may not be enough. The proposed testimony is more significant when it materially challenges an important part of the prosecution's evidence.
Can strong cross-examination reduce the importance of a rebuttal expert?
Yes. Mackoon illustrates that when counsel has already exposed many of the same weaknesses a proposed expert would address, a court may conclude that the additional testimony would not have created a reasonable probability of a different result.
Why is an ineffective-assistance claim harder on federal habeas review?
When a state court has already adjudicated the federal claim on the merits, 28 U.S.C. § 2254(d) limits the circumstances in which a federal court may grant habeas relief. The petitioner must satisfy the underlying constitutional standard while also meeting the applicable federal habeas requirements.
The procedural posture of Mackoon matters because the federal district court was reviewing a state conviction under 28 U.S.C. § 2254.
When a state court has adjudicated a federal claim on the merits, § 2254(d) sharply limits federal habeas relief. A petitioner must show that the state-court adjudication resulted in a decision that was contrary to, or involved an unreasonable application of, clearly established federal law as determined by the U.S. Supreme Court, or was based on an unreasonable determination of the facts in light of the evidence presented in the state-court proceeding.
The district court concluded that Mackoon had not met that standard.
During post-conviction proceedings, Mackoon presented a letter from forensic pathologist Dr. Mark Taff, who questioned the value of the surveillance footage for medical diagnostic identification. He cited problems including blurriness, black-and-white footage, and the camera angle.
Those criticisms did not directly address Dr. Termanini's central opinion. The State expert focused on whether the person's arm and hand movements were consistent with Mackoon's physical limitations, not on conventional identifying characteristics.
The appellate court therefore concluded that Dr. Taff's proposed testimony would have added little new information directly addressing that opinion.
Trial counsel had already raised several of the same criticisms during cross-examination.
According to the court's opinion, counsel established that Dr. Termanini:
Defense counsel returned to the video quality and other limitations during closing argument.
The post-conviction court described the cross-examination as vigorous. The jury also viewed the surveillance footage and was instructed that it did not have to accept the expert's opinion.
The federal district court focused on whether the New Jersey Appellate Division had unreasonably applied Strickland in rejecting Mackoon's prejudice argument.
The state court concluded that Dr. Taff's proposed testimony did not materially undermine Dr. Termanini's central opinion and that many of the same criticisms had already been developed through cross-examination. It therefore found no reasonable probability of a different verdict.
The federal district court held that this determination was not an unreasonable application of Strickland and denied habeas relief on the claim.
Mackoon does not mean that failure to consult or call an expert can never support an ineffective-assistance claim.
The district court contrasted Mackoon's case with Showers v. Beard, 635 F.3d 625 (3d Cir. 2011). There, a forensic pathologist testified during collateral proceedings that the lethal dose of liquid morphine could not have been administered surreptitiously or forcibly and that Showers's husband likely committed suicide. The Third Circuit affirmed the district court's grant of habeas relief.
Showers also involved appellate counsel's failure to raise trial counsel's omission. The Third Circuit concluded that the underlying trial-counsel claim had merit and that appellate counsel was ineffective for failing to preserve it.
The key difference was what the omitted testimony added. In Mackoon, the proposed expert did not directly rebut the State expert's central opinion. In Showers, the omitted expert challenged a central prosecution theory and supported a materially different explanation of the death. The comparison shows why the substance of the missing testimony matters more than the mere absence of a defense expert.
When specialized testimony becomes important in a criminal case, counsel may need to consider whether another expert would provide genuinely new analysis or mainly repeat points that can be developed through cross-examination.
Relevant considerations may include:
These considerations do not replace the fact-specific Strickland analysis or applicable procedural requirements. They help distinguish potentially significant new evidence from largely cumulative criticism.
Mackoon illustrates the importance of considering whether a proposed rebuttal expert's analysis directly addresses the opinion being challenged. The State expert focused on orthopedic conditions, biomechanics, and observed movement, while the proposed forensic pathologist focused mainly on the video's limitations as an identification tool. Depending on the issue, meaningful rebuttal analysis may require reviewing medical records, imaging, measurements, surveillance footage, and the materials or processing used in the challenged analysis.
The expert's role is to analyze those specialized issues. Whether counsel's performance amounted to ineffective assistance remains a legal determination for the court.
Can failing to hire an expert witness constitute ineffective assistance of counsel?
Yes, in some circumstances. A defendant generally must satisfy both parts of Strickland by showing constitutionally deficient performance and a reasonable probability that, but for counsel's deficient performance, the result of the proceeding would have been different.
Must defense counsel hire an expert whenever the prosecution uses one?
No. The Supreme Court has not imposed a categorical rule requiring a defense expert whenever the prosecution presents expert testimony. Depending on the circumstances, investigation, cross-examination, and other trial strategies may be relevant to whether counsel acted reasonably.
What must a defendant show about an expert who was not called?
The circumstances matter, but identifying an expert who disagrees with the prosecution's expert may not be enough. The proposed testimony is more significant when it materially challenges an important part of the prosecution's evidence.
Can strong cross-examination reduce the importance of a rebuttal expert?
Yes. Mackoon illustrates that when counsel has already exposed many of the same weaknesses a proposed expert would address, a court may conclude that the additional testimony would not have created a reasonable probability of a different result.
Why is an ineffective-assistance claim harder on federal habeas review?
When a state court has already adjudicated the federal claim on the merits, 28 U.S.C. § 2254(d) limits the circumstances in which a federal court may grant habeas relief. The petitioner must satisfy the underlying constitutional standard while also meeting the applicable federal habeas requirements.
Expert Witness Guides
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