Depending on the nature of the ligature and the amount of force inflicted, the intensivity of the contours will differ or will be merely latent. A well contoured ligature may display negative imprints. If the ligature slips upwards it can leave a second ligature mark. This can force lymph fluid upwards so that blisters are left above the ligature marks.
The ligature imprint is not conclusive proof of a vital incident.