There are some steps you can take to verify or disprove family stories of scoundrels and blackguards. Determine where the alleged event took place and what time frame. What county or governing area existed then? Remember that county lines are frequently redrawn as more people move into an area. New counties are created and territories become states.
The second step is to determine the nearest newspaper to the event in that time frame. This can be difficult because so many papers have gone out of business, been bought out, or just disappeared. Many papers that buy out another paper do preserve the archives. Libraries also frequently have archives of the largest papers in the area.
Once you have determined the likely county seat or equivalent, and the likely largest paper there, it is time to pay them a visit. If the event was notorious, the paper will probably have covered it. It may take hours of careful examination of microfiche, but you will probably be able to find a news article or some mention of the event. The Internet has made things a bit easier, as some papers are putting their collections on the internet.
It is important to understand that newspapers sensationalize things to sell papers. That was as true then as it is now. You may find a huge article on "the crime" and miss a small paragraph on "the acquittal." So try not to get too upset when finding lurid accounts of an event involving one's ancestor. Of course, some of us have those who really did do something shocking.
Once you have a newspaper account, however shocking, you have a definite date and some facts to work with. At this point, you can go to the county historical society, if it has one, and see if they have any information about the event or your ancestor. If the event was notable enough to make the paper, they probably do. Every place you can gather some facts helps you sort out what really happened. Look at this as a giant jigsaw puzzle where the pieces are hidden and must be found in order for you to assemble the puzzle and get the whole picture.
Probate records sometimes have interesting clues. Wills that exclude a family member or contain conditions for the disbursement of assets can hint at trouble. Some wills were pretty much confessions written on a death bed or before execution, in the old days.
Finally, you can try the criminal courts. The criminal court district is much larger than a county, but the district court clerk for the county seat can help you figure out what court would have heard that case. Unfortunately, unless there is an appeal, there will be only a bare-bones court record. It will record when the trial took place, when the various motions were heard, and what the disposition of the case was. If there was an appeal, though, you will get a wealth of information. It will cost you a wealth of money to get copies, though. A dollar a page is common, and the case may run 400 pages. However, in the testimony, you may find relatives you did not know existed. If the case is old enough, your relative may have signed the court record to indicate being sworn in. Holding the page your ancestor signed may make it all worthwhile.
In our case, we found that my great grandfather shot a man in self defense. The other cousin's story was wrong, and our great-grandfather was not a murderer. However, it took about four years for us to find that out. Nothing is fast when researching this type of tale.