Suit & tie is the way to go. You are trying to get a job as an LEO. ANY time you go for ANY reason for interviews, whether it be an Oral Board, BG investigation, or even just a "We want to go over your application one more time with you, would you come in real quick?" Wear a Suit & Tie. When I was going through the hiring process at my Department, my BI said "This will just be real quick, don't worry about dressing up..." I still went in cleaned up, squared away, and a suit and tie. I took it as a test, perhaps it wasn't. But nevertheless, it won't hurt....
Aoccdrnig to a rscheearch sudty at an Elingsh uinervtisy, it deosn't mttaer in waht oredr the ltteers in a wrod are, the olny iprmoetnt tihng is taht the frist and lsat ltteers are in the rghit pclae. The rset can be a toatl mses and you can sitll raed it wouthit a porbelm. Tihs is bcuseae we do not raed ervey lteter by it slef but the wrod as a wlohe. Initsenretg!!
Believe None of What You Hear, and Half of What You See.