A new oath holds pretty well; but... when it is become old, and frayed out, and damaged by a dozen annual retryings of its remains, it ceases to be serviceable; any little strain will snap it.
Even the clearest and most perfect circumstantial evidence is likely to be at fault, after all, and therefore ought to be received with great caution. Take the case of any pencil, sharpened by any woman; if you have witnesses, you will find she did it with a knife; but if you take simply the aspect of the pencil, you will say that she did it with her teeth.