Since you have all packs, that means you have Seasons which gave us hot and cold weather clothing categories. Sims arriving on a lot usually are dressed in the appropriate clothing for the weather. I have found playing the detective career, that the clothes won't match the clues if the weather is hot or cold out. From what you described; I think this is what might be happening to you. So, it pretty much comes down to using just the age, gender and hair color to find the right suspect a lot of the time.
Hope this helps.
