When you are taking a photo, and there is a bright light in the background, such as sunlight coming through a window, strange results may occur. This can happen with any camera, but it is especially prominent with cell phone cameras. Cell cameras are just not as good as regular cameras at rendering photos, mainly because of their image aliasing, and their generally poor ability to compensate for different lighting conditions.
When taking a photo in a back lit situation, people in the frame in the background can become dark, shadowy and blurred, giving the appearance of a spooky “shadow figure”.
I have included a photo that I took with my iPhone 5s, in my own home. I have not adjusted the photo post-camera in any way. It is straight off my phone, with no filters applied. The “shadow figure” is my daughter, alive and well. She is completely dark and shadowy, and her movements are blurry and distorted.
While this makes for a very creepy photo, it is not paranormal. Sometimes people can be in your photo frame without you even realizing they were ever there. Next time you see this type of image in a photo, compare and see if any of the above factors fit the situation.