I came from another state prior to LPD then LMPD. We did our own BA on DUI's and it worked great. There was a time frame but what a DUI comes down to is the driver was doing when we pulled them over, not what their BA was later in the night / day. As we all know a person's BA can either go up or down in that time frame and in this county that can make or break your case. In other states it is argued that the person's BA was lower when they were pulled over if the BA is anywhere near the legal limit.