Charles Marzyck is an interesting subject. The common belief of many relatives of the Showman family is that Marzyck killed the entire family because he was secretly in love with Pauline (his sister-in-law) and she did not return the feeling. In a rage of passion he struck the entire family down and then was able to escape justice. The other theory, the one advanced by the prosecution at the trial, was this was an act of revenge on those he felt had wronged him and sent him to prison.
There are a couple of questions that come to my mind here. The first I already touched upon; why did James and Minnie Vopat not show for the trial? I am not a profiler nor am I a psychologist (and maybe I should leave it at that but...my blog, my rules) but it seems to me James and Minnie were genuinely frightened of Marzyck. I believe there was a love triangle involving Marzyck but it was between him, Minnie and James. Marzyck had been involved in a few criminal enterprises before his prison term, all non violent and all the product of a "con." Bad checks, forged checks and a possible event involving the sale of tobacco that wasn't entirely his to sell*. The crime that got him "cheesed" was stealing wheat. The victim was James Vopat. Pauline may have testified against Marzyck in that trial but Will Showman clearly felt Marzyck had been wronged somehow. While in jail awaiting the trial, Will would visit Charles and bring him tobacco and food. While in prison, Will wrote letters and petitioned for his release as well as corresponding with Marzyck. These are not the actions of a man who's wife's life had been threatened.
If Marzyck followed his previous MO then the "theft" was likely that of fraud. A bad check or possibly paying half the money owed for the full order of wheat then selling the wheat elsewhere and skipping town with the money (the scam run with the tobacco in Denver). Minnie may have had enough of her husband's dishonest ways and confessed the crime to Vopat and Sheriff Bradshaw. If this is the case then not only did Minnie betray her husband but then she married the man he had tried to swindle, a double betrayal. This explains the actions of Marzyck during the murder trial. He practically burned holes in the heads of the Vopats during their testimony. Clearly Marzyck's beef was with the Vopats and not the Showmans. But Will Showman was a good and honest man by all accounts and it's hard for me to believe he would have taken up the cause of a person he believed to be a genuine criminal. Not to get to close to tin foil hat territory but the possibility exists that Marzyck was set up by Minnie and James in order to get him out of the way of their relationship. Clearly the authorities believed a piece of evidence, the cigar cutter, was planted. Conveniently this cigar cutter was IDed by Minnie Vopat as belonging to Charles.
I must stress that I DO NOT think the Showman's were killed in order to frame Marzyck and put him away for good. So James Vopat is not a suspect and shouldn't be considered at all; neither should Minnie. But should Marzyck? While his alibi put him in Denver at the time of the Ellsworth murders, it also put him within a short train ride of Colorado Springs. If Minnie is to be believed, then Marzyck also had relatives in Monmouth, Illinois. He represented himself in a trial that if lost, would have certainly lead to his swinging from a gallows so he was level headed. If I were to find out he was a gandy dancer for a railroad I'd say he was a great suspect. But Charles was a "clever" fellow and was a good talker. His crimes relied on his ability to convince others he could be trusted and he was comfortable talking to people. His crimes were that of the lazy man; working hard to con a person out of a few bales of wheat without realizing his talent for selling ice to Eskimos. The killer of the Waynes, Burnhams, Dawsons and Showmans had no such ability. He had to attack his victims in their sleep because he wasn't confident enough to get them while they were awake. Further, Marzyck had no history of violence (although he was said to be a nasty drunk) and the life of the con man is to get the money or items and get the heck outta there. I believe Marzyck was innocent of this and the other crimes but I can't rule him out completely; he's just to tempting a character.
*Turns out this may have been his father