Corporate Manslaughter

Hi all, got a law question for you all.
I am currently freelancing for a company doing web design, no contracts or anything have been signed.

They have me working on a system for the NHS which will allow people to escalate issues to their managers and their managers managers etc.
At the time of undertaking the job the system was not going to be used in a court of law but now it is if needed. In cases like corporate manslaughter.
The question I’m asking is who would be liable if the system failed and escalations were not sent to managers and because of that someone died?

For example:

If someone knows that there is legionnaires disease in one of the water tanks and they use the system I’m developing to tell their manager that they have a problem and for some reason the system fails and never sends out an email to the manager. Because of this the tank is never fixed and someone dies. When the case comes up in court who would be liable for the death, would it be the first person because the just relied on 1 system to get it fixed or me who developed the software which failed?

Hope that made sense.

Thanks