sash - but with medical trials, doctors, nurses and other NHS staff have professional codes of conduct, which say they must always act in the best interests of the patient, always seek consent, respect confidentiality etc etc. Performing clinical trials without consent, involves breaching confidentiality and goes against the NHS constitution, which includes such things as dignity, respect etc.
Your remark about still checking someone is dead 3 months after they've died trivialises the argument - of course someone will still be dead three months after they've died. My point is, the researches should inform relatives that their loved one has been involved in a trial, and seek consent to include that data in the trial. Likewise, if a survivor withholds consent, the data already gathered from them before they've been able to be asked for their consent should not be included in the trial.
Researchers being scared of upsetting relatives is not a good enough excuse not to seek consent, and fears of skewing the results should not be a good enough excuse to ignore patient preferences regarding consent about data already gathered.
People have died in wars to protect individual freedoms, and if people have to die to protect patient freedoms and autonomy from researchers, doctors, nurses and other unscrupulous NHS staff, then so be it. All for the simple discourtesy of not asking for permission to use your data.