Hopefully, this will clear things up for you The_DADDY
When a person dies, in most cases a doctor writes a medical certificate of cause of death (MCCD) which is then recorded in the death registration (at a local authority registration office). The details are printed out as the official 'death certificate' for the next of kin. The same information is sent electronically from the registration office to ONS for us to produce statistics about causes of death. For some deaths, such as when the death was due to an accident or violence, there is a coroner's inquest to establish the facts and the coroner then decides the cause of death and sends their findings to the local registrar.
The doctor or coroner certifying a death can record more than one health condition or event on the form. The medical certificate of cause of death has two parts, Part 1 contains the sequence of health conditions or events leading directly to death, while Part 2 can contain other health conditions that contributed to the death but were not part of the direct sequence. For statistical purposes one of the health conditions on the certificate is chosen as the 'underlying cause of death'. The underlying cause of death is defined as the health condition or event that started the train of events leading to death and is worked out according to rules from the World Health Organisation (WHO). COVID-19 is the underlying cause of death in around 92% of deaths where it was mentioned on the death certificate.
If someone dies in circumstances involving an accident, violence or suspicious circumstances, the case is referred to a coroner for investigation. A post-mortem examination is carried out and usually an inquest is held. The Coroner's Court hears all the evidence and follows legal rules of evidence when deciding the causes of death. It is extremely unlikely that a coroner would find that someone was involved in a traffic accident, or was the victim of violence, because of having COVID-19 or a positive COVID-19 test -- so they would not mention COVID-19 on the death certificate. This applies to any death caused by an accident, violence, poisoning, or other external causes.
Even if in an unusual case a death certificate mentioned both COVID-19 and a traffic accident (or other external causes), the World Health Organisation (WHO) rules for coding deaths mean that the traffic accident would be identified as the underlying cause of death in our data.
You can read in detail about the coding of causes of death and identifying the underlying cause in the ONS User guide to mortality statistics and the WHO International Classification of Diseases (ICD-10) instruction manual.