New images of a case believed to be for the Samsung Galaxy S8 have surfaced and they appear to show a fourth physical button will be present on the device. The question then is what that button may be used for with some sources suggesting Samsung will use it as a trigger for their own assistant technology called Bixby. Presumably that would be used at times when voice control is not possible or desired. The images show this fourth button on the right hand edge of the device opposite the left hand edge that appears to hold the typical configuration of power button and volume rocker buttons.
Besides the addition of a fourth button, sources have also noted the absence of a cutout for a fingerprint scanner on the device. With the display apparently slated to dominate the front of the device, no space is available for a home button/fingerprint scanner. Potentially the fingerprint scanner could be located underneath the front glass display if Samsung employs new technology developed by Synaptics.
Another alternative to the Synaptics solution is that the fingerprint scanner is located next to the camera lens on the back of the device. The cutout for the camera appears to be unusually large in these images. If accurate, this may suggest other items located on the back of the device. This could include a fingerprint scanner and some are suggesting a heart rate monitor as well.