It will depend on the organization. The need for a separate safety professional or department often comes out of a growing company because in smaller companies, HR wears that hat in many cases especially with claims reporting. So it is a natural development in a growing organization.

I would start with understanding who is communicating the claims to the insurance company. Change is not easy, but at the end of the day, departments are often willing to give up additional responsibilities unless they are in need of validating their employee count. No matter what, safety should be involved.

Refer to your organizations HSE roles and responsibilities Policy. If your in Calif, then it willbe in your IIPP. Typically Safety owns investigations.; however HR may have roles in working with Workers Comp adjusters to track LTI and RTIs. This can sometime lead to bleed over into other programs such as Short Term Disabilities PTO, Long Term Disability, etc. . Usually when HR gets involved is usually to determine work -relatedness for workers comp issues. They should not be getting involved in root cause analysts.
Another area of concern will be in the form of discipline. for safety related incidents. Although OSHA likes to see programs that outline enforcement processes (rules of conduct and associated discipline), this inherently brings HR into play. In my opinion Safety professionals should provide tools to the immediate manager to help them make the best decision that best suits their needs. If they decide to discipline, the refer them to HR on what's the next step is based on the companies progressive discipline policy or state employment law.

In my company I report to the VP of HR. I work closely with the entire HR team in not only investigations but other aspects of the safety program. While I am the expert on safety within the company they are willing to help and support as needed to ensure we create a safe culture.

Safety and HR should work together as both are support staff for management. Safety needs rules and regulations, HR needs to understand and support those rules. Most HR professionals have no training in Safety issues such as incident investigation. The best companies I have worked for understand this and work together.

Very little involvement between HR and Safety unless there is an injury involving time away or workers comp, which is pretty rare. The fact your HR department is blindsiding you on incident investigations is a huge red flag. I'd work this out with you supervisor

HR is typically not involved with safety except for new hire trainings and in cases of severe non-compliance. We have a fairly large safety organization, so we handle the investigations with the employee, manager, and witnesses.
Pandemic caveat: we currently work rather closely with HR due to COVID.

It should be a partnership, but i have worked at a place which gives HR more authority and respect than safety. It definitely puts you in a tough position.

In my previous company, our HR team was very hands off. I often times found myself taking on tasks that were actually the responsibility of HR. I think that having HR involved could be an awesome partnership for you, but they have to understand that incident investigations are a team effort and should be led by the SMEs. HR should really only play a role in any employee relations problems that are identified in investigation findings (in my opinion).

My first job me and HR worked well together. Mainly working with them on Workers Comp. My current job we do not do much with HR. Mainly communicate with them about new hire training. How long have you been there?

Entirely from a UK perspective, but i and my team work closely with HR, and there are naturally shared aspects in what we do. However, with respects to leading an accident investigation it should be the person who has competencies to do so - skills, experience and qualification - which usually would be found within you H&S professionals. You wouldn’t expect janitor to start teaching because they work in a school. Equally, this separation is important to ensure that there is no perceived bias, particular relevant should there be any civil or criminal litigation as a result of the incident l.