You don’t make much of a case except to just say its a fraud. Those who claim it is authentic have a great abundance of evidence from a variety of scientific disciplines to support their claim.
If it is a fraud after all, it is a doozy. The fraudster would have had to put actual blood on the shroud where the scars are. He would have had to duplicate all of the scars in exact detail front and back, knowing exactly what type of whip the romans used in that day and then knowing how to duplicate the type of scar the whip would leave. He would have had to have known the exact size of Roman spears in that day so he could duplicate the spear wound in Jesus’s torso. He would have had to collect pollen and flowers from jerusalem and put them on the Shroud. He would have had to paint the image in such a way that it contained three dimensional holographic information. He would have had to have known of the concept of a negative image hundreds of years before the invention of photography and then, just for fun, have decided to paint in a negative image because it would make the image seem more real. He would have had to have painted the image in such a way that only the outermost fibres contained the pigment. He would have had to have rejected the common belief that Jesus was nailed through the hands and decided he was nailed through the wrists instead. He would have had to have applied the real blood stains in such a pattern that they exactly matched the blood stain pattern on the suderium (face cloth) AND he would have had to have known to use the exact same blood type as the blood on the suderium.
And he would have to arrange that the carbon 14 date would match the 12th Century.