Does your acquired disk image refuse to mount on the desktop? If you have selected the option to turn off Disk Arbitration when MacForensicsLab launches or disabled Disk Arbitration by selecting the option from the Window menu, Disk Utility will not be able to mount any images until Disk Arbitration is turned back on. This issue can be resolved using either of these options.
Re-enabling Disk Arbitration can be done either by selecting the Disk Arbitration option from the Window menu within MacForensicsLab again and enabling it or by rebooting your Mac. Many times Disk Arbitration can be turned off and forgtten about because of MacForensicsLab's ability to see drives at the device level. This means you can still work with disk images within MacForensicsLab even without mounting them on the desktop as you normally would. If you're still having problems mounting disk images after re-enabling Disk Arbitration in MacForensicsLab restart your computer.