The fact that everything else in the photo was blurry due (my guess) to being taken at night without flash nor tripod (I love take night photos without flash, but if I am not careful mine also turn out like this), yet the "artifact" lines are crisp leads to the artifact not being in the original image (unless the ghost managed to vibrate at the same frequency and time as the shaky photographer)
This leads to 2 options, Deliberate insertion or double/half exposure. Was this photo taken on a digital or Film camera? I have a lot of old Photos like this on my SLR where I failed to wind the film on fully, giving and extra half exposure on one side. If it was film, I would look at the negatives and see what the next photo was of, If it was a digital, Get a hold of the original and look at the EXIF data of the photo and see what has been used to edit it