Co-ed detective shows??? Hmmm, cannot say I know what exactly you mean? Are you inferring that because a woman (who also might be a detective) is featured along with the men, that it then becomes a "comedy"?
If so....hmmm, I have seen some really tough women portrayed...Ziva on NCIS for instance. And...well, the great Alfred Hitchcock always said that you have to relieve the excitement/suspense with something light for the audience, even if it only lasts a minute or less. He felt that it was absolutely necessary.