You already know you need to get to a good in fact a very good CRIMINAL DEFENSE ATTORNEY. You should look for one in the county this happened in. If it is a small county then go to the nearest big city.There are a lot of really good lawyers in Houston.
Ask the lawyer if he has any experience working on Vehicular homicides. Find out how long he is in practice. (I would think you would want someone with at least 15 years experience on this type of case).
Find out if the lawyer you pick has gone to trial on at least 25 cases. Also find out if he is an active member of either NACDL or TACDL the national and state affiliate of criminal defense lawyers. Harris County has a pretty good Criminal defense bar association too.
Does the lawyer give speeches to other lawyers and if so has he ever spoken on issues dealing with criminal charges derived from traffic accidents or DWI. If he has spoken but not on your issue, that is a good thing. It means his colleagues respect his knowledge. If he has spoken about your issues that is icing on the cake.
Find out if he has written anything on the subject of your case. Again if he is a published author he is already ahead of most attorneys, if he has written an article about the issues your husband's case presents then that is just serendipity.
Finally, make sure he has an office proceedure you can live with. Find out about his billing method, his policy on return phone calls, e-mail. Are there ancillary costs such as private investigators, engineering experts design experts and the like.
I hope this will help you once you have identified the attorney you want to represent your husband.
ONE MORE IMPORTANT CAVEAT: DO NOT LET YOUR HUSBAND SPEAK TO ANYONE BESIDES THE LAWYERS YOU ARE INTERVIEWING, UNTIL YOU HAVE HIRED A LAWYER AND HE IS AWARE OF WHAT YOUR HUSBAND IS BEING ASKED AND HOW HE WILL ANSWER.
It sounds like your husband's company is doing all the right things. In fact his interest is the same as theirs. If he's found criminally negligent they will most likely have to pay the civil damages. Don't worry too much about the trooper's report; this one will be decided by accident reconstruction experts. If you still feel insecure hire your own lawyer but for the time being you'll just be duplicating charges. Wait and see what the company's attitude is: if they start acting like they are going to cut him loose, get your own lawyer ASAP. In the meantime as the other lawyer says your husband should keep his mouth shut. Many people talk thinking they can convince others of their innocence. Instead they are only digging a deeper hole for themselves.
I am answering months after you asked so I will say this - if you find that during the course of this case, your husband is not having his questions answered, or that the answers are evasive, hire at least additional counsel (and perhaps counsel to take over.)
By this time, you should have much discovery finished on the case - accident reconstruction report by your own expert, witnesses all interviewed again (not just reliance on the report), photographs of the individual autos.
I disagree that your lawyer should have 25 trials. Some lawyers who handle these type of cases rarely go to trial because they have proven themselves (and their experts) to be close to impossible to beat in just a few cases. As you explain it, it sounds like your husband's case may not be that difficult. That said, his income & livelihood depend on his job, and at this point, a good lawyer.
Your husband has the right to answers. Feel comfortable with the lawyer, or seek additional advice.