As a private investigator that specializes in surveillance, I face certain challenges on a regular basis. Our detective agency has came up with ways to deal with these situations. One such issue is shooting video through a rain soaked window.
You can not shoot good video through a rain soaked window, with a cheap camcorder.
The problem with cheap camcorders is that they do not have a good manual focus. They may have a manual focus that you access through menus, but that is not acceptable when video needs to be obtained quickly. In regards to camcorders, under $2,000 is what I mean by cheap. A cheap camcorder is great for non professional applications such as video of the family. But not for surveillance.
The camcorder we use is the Sony VX2100. You can do a search for it on Google. It features a manual focus ring. I have gotten video through windows so soaked with rain, that I could not see through them with out the use of the camcorder. The Sony VX2100 can be purchased from Sony directly at www.sonystyle.com for $2,999.00. I recommend the zoom lens as well for an additional $400.00
Another tip for getting video through window in the rain, is to shoot the video through the side window of your vehicle. Because of the angles of those windows, rain water doesn't stay on them like it usually does the front or rear window.
I strongly recommend asking a private investigator you are hiring, what type of camcorder they use. Ask the model #. If they don't know, that is a bad sign. If they give you a model, research the camcorder online. Professional equipment will make the difference between video you can use in court, or sometimes not getting video at all.