Shadows make our screen shots look better. But we can’t always use them. There are times when we need to go ahead and disable them due to some reason or another. If you need to disable the shadows on screen captures, you can do so using the following command:
defaults write com.apple.screencapture disable-shadow -bool true

To then enable the shadows, you would use the following command:
defaults write com.apple.screencapture disable-shadow -bool false