For mounting images, first check the image structure, using the following command:
sfdisk -l evidence09_sdb.dd
You will obtain something similar to this:
The partition starts at the sector 63. This multiplied by it size (512) gets that the block we have to use is: 32256.
Therefore, the command to run is:
mount -o ro,loop,offset=32256 evidence09_sdb.dd /mnt/evi09mnt
Note: create the folder evi09mnt before.
Further information
here.