An EMT may decide to pronounce death when:

An EMT may decide to pronounce death when there is a valid Do Not Resuscitate (DNR) certificate present. A DNR is a legal document that indicates a person's wishes regarding resuscitation attempts in the event of cardiac arrest or respiratory failure. If a valid DNR certificate is available, it means that the patient has previously made a decision regarding their desire not to receive certain life-sustaining treatments, including cardiopulmonary resuscitation (CPR).

In cases where a DNR is present, the EMT can confidently determine that the patient's wishes should be honored, and no resuscitative efforts need to be initiated. This aligns with the ethical and legal responsibilities of EMS personnel to respect a patient's autonomy and end-of-life choices.

The other scenarios provided do not authorize an EMT to pronounce death. Family members requesting the pronouncement does not carry the same weight as legal documentation. Visible signs of improvement would necessitate ongoing assessment and treatment rather than a pronouncement. Lastly, a conscious and communicative patient who is still alive would require medical attention and would not be suitable for a death pronouncement. Thus, the presence of a valid DNR certificate is the correct basis for an EMT to determine that a patient has died.