U.S. Diplomat's Wife Charged In Crash That Killed British Citizen

The transcript discusses the incident involving the death of 19-year-old British motorcyclist Harry Dunn, who died after a collision with an SUV driven by a person who returned to the US under diplomatic immunity. The UK has initiated extradition proceedings after the driver was formally charged, but the driver's attorney stated she will not return voluntarily to face potential jail time for what is described as an unintentional accident.

What does the term 'diplomatic immunity' refer to in this context?

How did the authorities respond after the incident involving Harry Dunn?