I have a science degree, spent considerable volunteer time in a crime lab, have taken additional crime scene related classed, ie; serial # restoration, minor crime scene investigation, etc, have had 5 job interviews, placing second in two of them, to people who volunteered within that particular agency. Is there more of a catch than having a degree and experience?
Sometimes there is. In your situation the jobs went to people who had volunteered in that agency and you, with all your training and experience, came in second. What often happens is that the hiring agency has had time to evaluate the volunteer who has been working right there in their department and they decide that they are comfortable giving that person the job. You see, they really don't know how you will work out until they see you on the job, so hiring anyone they don't really know does involve a measure of risk.
But be sure: not all volunteers will be selected for the job in the departments where they volunteer. Many times the department keeps a volunteer (they give the department a lot of free hours of work) but would prefer someone with more training and experience--or just someone else--for a permanent position.
You are definitely doing the right things by taking classes and volunteering in a crime lab. That shows by your #2 placements when another candidate has the edge.