### **Fact-Based Summary: Byron Black's Execution**  

#### **1. Execution Protocol & Events**  
- **Method**: Lethal injection (Tennessee’s standard three-drug protocol: midazolam, vecuronium bromide, potassium chloride).  
- **Observed Physiological Response**:  
  - Black exhibited **audible distress** ("It's hurting so bad").  
  - Heavy sighing, groaning, followed by loss of movement at **~10:36 AM**.  
  - Pronounced dead at **10:43 AM**.  

#### **2. Implanted Cardiac Device (ICD) Considerations**  
- **Device Function**: Designed to detect and correct life-threatening arrhythmias via electric shocks.  
- **State’s Position**: No confirmed deactivation prior to execution.  
- **Medical Uncertainty**:  
  - If ICD fired, it could have temporarily restarted Black’s heart after KCl-induced VF.  
  - No official data released confirming whether shocks occurred.  

#### **3. Potential Causes of Distress**  
Based on **established pharmacological and medical principles**:  

| **Factor**               | **Possible Contribution to Distress** |  
|--------------------------|--------------------------------------|  
| **Midazolam (sedative)** | Inadequate sedation → consciousness during execution. |  
| **Potassium Chloride**   | Chemical irritation of veins → burning pain if IV placement imperfect. |  
| **Vecuronium (paralytic)** | Respiratory arrest → air hunger if sedation insufficient. |  
| **ICD Intervention**     | If shocks occurred, could cause involuntary muscle contractions. |  

#### **4. Key Unanswered Questions (Lacking Data)**  
- **Was the ICD active?** No official confirmation from execution records.  
- **Did it deliver shocks?** Device logs were not released.  
- **Sedation depth?** No EEG or consciousness monitoring reported.  

#### **5. Documented Precedents in Lethal Injection**  
- **Midazolam failures**: Observed in other executions (e.g., Clayton Lockett, Oklahoma 2014).  
- **KCl pain**: Reported in cases with poor IV administration.  
- **ICD interference**: No prior documented cases in executions.  

#### **6. Conclusion: What We Know vs. What We Don’t**  
- **Known**:  
  - Black displayed distress consistent with **potential midazolam/KCl complications**.  
  - The ICD introduced an **uncontrolled variable**, but its impact remains unverified.  
- **Unknown**:  
  - Whether the ICD prolonged the process.  
  - Whether pain was purely drug-related or device-augmented.  

#### **Final Takeaway**  
Byron Black’s execution followed Tennessee’s established protocol, with **observed physiological responses** that align with **known risks of lethal injection**. The ICD’s role—if any—was not confirmed by authorities.  

For a definitive assessment, **autopsy toxicology and ICD logs would be required**, but those have not been made public.