Need for Criminal Investigation

1. Accountability: Identifying and prosecuting those responsible for the distribution of lethal drugs holds individuals or groups accountable for their actions.
2. Deterrence: The possibility of facing criminal charges acts as a deterrent for potential offenders.
3. Justice for Victims: Provides closure and justice for the families of drug induced homicide victims.
4. Public Safety: Helps remove dangerous substances and offenders from the community, enhancing public safety.

Necessary Protocols

Initial Response and Scene Management

1. Immediate Medical Assistance: Prioritize life-saving measures while minimizing disturbance to the scene.
2. Securing the Scene: First responders must secure the scene to preserve evidence.
3. Notification of Relevant Authorities: Inform law enforcement and specialized drug investigation units immediately. 

Evidence Collection 

1. Physical Evidence: Collect any drug paraphernalia, substances, and containers present at the scene.
2. Electronic Evidence: Seize and examine electronic devices that may contain communication related to drug transactions. Identify victim login and passwords, if known. Collect camera footage that may show suspect(s) or victim in the time surrounding the death.
3. Forensic Evidence: Perform a thorough forensic examination, including toxicology reports, to identify the substances involved.
4. Witness Statements: Record statements from witnesses, if any, at the scene or known to the victim.

Follow-Up Investigation  

1. Chronological History: Establish victim timeline of events prior to death.
2. Background Checks: Investigate the victim’s history for prior drug use or connections to known dealers.
3. Social Media Content: Deploying preservations, subpoenas and warrants collecting social media data.
4. Surveillance and Informants: Use of special investigative tools such as controlled delivery, undercover operations, and electronic surveillance.
5. Financial Investigation: Examine financial records of victim and suspect(s) for evidence of drug trafficking. Examine rideshare and tollway records of victim and suspect(s)

Necessary Elements for Successful Prosecution 

1. Proving Causation: Establish a direct link between the drugs supplied and the death.
2. Chain of Custody: Maintain an unbroken chain of custody for all evidence collected.
3. Corroborating Evidence: Gather corroborative evidence to support witness testimony.
4. Expert Testimony: Utilize expert testimony, especially in interpreting toxicology results.
5. Legal Compliance: Ensure all investigation methods comply with legal standards to avoid evidence being dismissed in court.

The criminal investigation of drug deaths is a complex but crucial endeavor. It requires a coordinated effort between various branches of law enforcement and the justice system. By adhering to strict protocols and gathering comprehensive evidence, law enforcement can build strong cases for prosecution, thus contributing to the fight against the illegal drug trade and its tragic consequences.