It makes little difference since you should explain at least three research projects you have completed/published and obtain a recommendation letter for each. If your work was used in the DOJ, obtain a letter of recommendation from them detailing how they used your work. In my situation, I received five recommendation letters: two from dependents who worked with me, and three from independents who used my work but did not collaborate with me. Obtain a letter of recommendation on their official letterhead if possible. I had 10 publications at the time of application, including journal and conference articles, and had accumulated around 80 citations. I would advise you to publish more of your work as a first author so that you can build up some citations.