---
title: "Internal Medicine Expert’s Testimony Partly Excluded Because He Made Credibility Determinations"
meta:
  "og:description": "Internal medicine expert must assist the trier of fact in determining credibility, not determine credibility for the trier of fact"
  "og:title": "Internal Medicine Expert’s Testimony Partly Excluded Because He Made Credibility Determinations"
  author: "Expert Witness Profiler"
  description: "Internal medicine expert must assist the trier of fact in determining credibility, not determine credibility for the trier of fact"
---

# Internal Medicine Expert’s Testimony Partly Excluded Because He Made Credibility Determinations

Posted on April 9, 2025 by Expert Witness Profiler

This is a medical malpractice case arising primarily out of the treatment provided to Plaintiff’s father, Santos González Ponce (“Mr. González”) at co-Defendant Doctors’ Center Hospital and Caribbean Medical Center (“CMC”) by Defendants Dr. Glorimar Santos Llanos, Dr. Glorimar Santos-Rodríguez, and Dr. Iolani García-Rosario  (“Dr. García”) at those medical institutions.

Plaintiff argued that Dr. [Miguel A. Colón-Pérez](https://expertwitnessprofiler.com/expert-witness/Miguel-Col%C3%B3n-P%C3%A9rez/1563656)‘s expert testimony should be excluded since his report, dated August 31, 2024, is not signed.  Second, Plaintiff posits that the expert report “is devoid of references to medical literature to support the opinions contained therein” and is only based on “the expert’s say so, without reference to medical authorities, textbooks or literature.” Third, Plaintiff contended that Pérez-Colón’s report improperly vouches for García’s credibility inasmuch his expert opinion relies on her own statement that she “never saw the blood cultures.”

## **Internal Medicine Expert Witness**

[Miguel A. Colón-Pérez](https://expertwitnessprofiler.com/expert-witness/Miguel-Col%C3%B3n-P%C3%A9rez/1563656) is board certified in internal medicine since 1989 and in infectious diseases since 1994. He is admitted to practice medicine in Puerto Rico and the states of Florida and Colorado. Colón-Pérez is also a member of various well recognized societies in his fields of practice, such as the “Infectious Diseases Society of America” and the “Socieded Panamericana de Enfermedades Infecciosas.”

[Get the full story on challenges to Miguel Colón-Pérez’s expert opinions and testimony with an in-depth Challenge Study.](https://expertwitnessprofiler.com/order/add?eId=1563656&amp;pId=3)

## **Discussion by the Court**

### **Qualifications**

Plaintiff did not contest Colón-Pérez’s qualifications. Based on the educational background and professional experience outlined in Pérez-Colón’s curriculum vitae, the Court found that they are sufficient to satisfy the requirement that a proposed expert witness be qualified by “knowledge skill, experience, training, or education.”

### **Expert Report “Prepared and Signed by the Witness”**

Colón-Pérez’s expert report is not signed. Yet, Plaintiff does not assert how the lack of signature is prejudicial. The absence of an expert’s signature is curable and renders the defect harmless. Consequently, the Court held that the exclusion of Colón-Pérez’s report is not warranted on this basis alone.

Colón-Pérez was directed to submit a subsequent affidavit adopting the statements in his previously submitted and unsigned expert report or to submit a signed expert report, on or before April 4, 2025.

### **Colón-Pérez’s Expert Report**

A thorough reading of the report demonstrates that Colón-Pérez did not directly cite any medical literature. However, throughout the report, Colón-Pérez references data and medical terms that certainly derive from his field of medicine. For instance, he states: “In the USA, lower respiratory tract infections surpass all other infections in terms of morbidity and mortality.” Furthermore, he notes, “In all cases of severe bacterial pneumonia, immediate initiation of empirical therapy is crucial to prevent sepsis. If left untreated, pneumonia can result in an overall mortality of up to 30%.”

Colón-Pérez concluded that “when the involvement of Iolani Garcia Rosario, in the care of Santos Gonzales Ponce, is evaluated in full detail, it is clear that the patient arrived at the hospital with clinical signs and symptoms of facial cellulitis.”

Ultimately, Colón-Pérez concludes that: “there is no deviation of the best practice of medicine by Iolani Garcia Rosario when her clinical analysis of the case, which was supported by the Infectious Diseases and Pneumology service, was that the most likely cause of the poor medical condition of the patient was due to the severe pneumonic process and this source of infection needed the most urgent care.”

The Court notes that an expert “need not necessarily cite literature or a published standard in demonstrating that he has relevant expertise. . .instead, his personal experience alone may be sufficient.”

Other than complaining about absence of reference to publications and medical literature, the Court found that Plaintiff did not specifically explain why the testimony in question was insufficient or unreliable as to show what was the national standard of care that applied in this case. Furthermore, the sufficiency of Colón-Pérez’s professional experience has not actually been challenged here.

### **Expert Testimony Regarding Witness Credibility**

The Court addressed Plaintiff’s claim that Colón-Pérez opinion improperly vouches for García’s credibility. In his report Colón-Pérez concluded:

“It is critical in this case that Garcia was never notified of a panic level of positive blood cultures w/ gram positive cocci on 11-24 and neither was notified on 11-27 when the final results of blood cultures showed methicillin-resistant Staphylococcus aureus.”

In this case, it is a contested issue of fact whether Defendant physicians evaluated certain blood cultures now included in González’s medical record at the CMC, and if those blood culture were available to the physicians, particularly García, at the time.

Certainly, Colón-Pérez does not directly say that García is truthful. Yet, he is giving weight to her version of events and reaching a concluding based, at least partially, on that version. The Court held that these statements in the expert report are unsubstantiated and speculative at best and would not assist the trier of fact. In other words, García’s expert must assist the trier of fact in determining credibility, not determine credibility for the trier of fact.

[Rule 703](https://www.law.cornell.edu/rules/fre/rule_703) was never intended to allow a witness, “under the guise of giving expert testimony, to in effect become the mouthpiece of the witnesses on whose statements or opinions the expert purports to base his opinion.

## **Held**

The Court granted in part and denied in part the Plaintiff Wanda I. González-Villegas’ motion_ in limine_ to exclude Defendant Dr. Iolani García-Rosario’s expert witness report prepared by Dr. Miguel A. Colón-Pérez.

## **Key Takeaways:**

- Determining the credibility of a witness is a function reserved exclusively for the jury. Regardless of whether an expert possess “medical knowledge and skills that relate directly to credibility,” they are barred from opining as to whether a witness is being truthful. In this case, Colón-Pérez does not directly say that García is truthful. Yet, he is giving weight to her version of events and reaching a concluding based, at least partially, on that version.

- Colón-Pérez need not necessarily cite literature or a published standard in demonstrating that he has relevant expertise here; instead, his personal experience alone may be sufficient. In sum, the medical records, combined with Colón-Pérez’s own clinical experience, provided a sufficiently reliable basis for his opinions.

- The absence of an expert’s signature in a report is curable and renders the defect harmless.

## **Case Details:**

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