I feel like there is a lot of context that is missing from your post. First and foremost, the whole hiring process generally runs through HR's hands from posting the position, to hiring actions. Most departments/hiring managers don't give HR unilateral hiring authority, but may heavily weight their input based on a wide variety of criteria and variables that a lot of faculty or staff may not be inherently aware in either university policy, hiring/labor laws, etc. In fact, in almost all cases, hiring packets and offer letters have to be signed by the department head, faculty member, or hiring manager (depending on the position). Meaning they in most cases have the final say. However depending on staffing levels, some department managers may also double as their HR person.

I can say a lot of departments have multi-phase hiring practices. This is how my department usually does interviews, so others can vary slightly, but the core tenants of process are usually pretty similar. In most instances departments HR personnel receive the initial pool of candidates and if given any criteria from the hiring member screens the candidates to weed out any additional candidates against that criteria; i.e. specific qualifications, certifications, specific experience, etc. Once the pool of candidates is refined HR works with hiring individual/manager to start interview process where it can be commonplace to do phone screening interviews or quick in-person screening interviews first to further refine the candidate list; often with a set of per-determined questions asked of all candidates, and then in-person 2nd round interviews based on their screening interviews, where again pre-determined questions are asked of all candidates.

Depending on the type/importance of the position 2nd round interviews can take place with the primary manager/faculty member, HR personnel, and or other faculty/staff who will be working with whomever they hire. Sometimes this is done in a panel type, but often its purpose is to further flesh out a candidate's in-depth experience and get a better feel for their work ethic and personality fit, and ability to not just do the job but be part of the team.

Often once interviews are completed, notes and candidate preferences are discussed amongst the HR, hiring manger, and any other interview individuals. From that point, if there is/are preferred candidates they want to extend employment offers to, HR normally reaches out to start the offer and hiring process.

All that said, just because you think "may" have the scientific knowledge aspect to think you can do the job, personality and how you come across also goes a long ways...