You gotta figure the police were going to charge Madame Carala with masterminding the murder of her husband, manipulating Julien to do the dirty work. Since she had been married to an arms dealer - which carries a connotation of ill-gotten gains, i.e. wealth derived on the backs of other peoples misery - you can bet there would be no public sympathy for her at trial. Whereas Julien, an ex-paratrooper who had fought in two of Frances recent wars (Algeria and IndoChina) would at least have public sympathy, as the paratroops were held in high esteem by the public. So its doubtful the police would have bothered with putting the entire guilt on him. Florence Carala was the bigger and juicier villain in this matter. The prosecutor would have sought, and probably would have gotten, a more severe sentence for her. A bit of politics involved, safe to say.
Now, with my machine, I cut your head off in the twinkling of an eye, and you never even feel it!
Joseph-Ignace Guillotin