I think people thinking they can discredit digital photos have no concept of metadata. Here's an example of the data embedded in each image file:
EquipMake Canon
EquipModel Canon EOS DIGITAL REBEL XT
Orientation 1
XResolution 72
YResolution 72
ResolutionUnit 2
DateTime 2005:12:08 14:45:36
YCbCrPositioning 2
ExifExposureTime 0.001
ExifFNumber 14
ExifExposureProg 2
ExifISOSpeed 200
ExifDTOrig 2005:12:08 14:45:36
ExifDTDigitized 2005:12:08 14:45:36
ExifShutterSpeed 9.96578979492188
ExifAperture 7.61471557617188
ExifExposureBias 0
ExifMeteringMode 1
ExifFlash 16
ExifFocalLength 200
ExifColorSpace -1
ExifPixXDim 3456
ExifPixYDim 2304
20545 R03
ExifFocalXRes 3954.23340961098
ExifFocalYRes 3958.76288659794
ExifFocalResUnit 2
41985 0
41986 0
41987 0
41990 0
42240 2.2
ThumbnailCompression 6
ThumbnailResolutionX 72
ThumbnailResolutionY 72
ThumbnailResolutionUnit 2
JPEGInterFormat 9716
JPEGInterLength 4668
It would take some wizard to alter this in a series of image files without introducing some inconsistency. Much less be able to upload the altered image back to the camera/phone.
particularly on a phone with the time being set by a NTP (Network Time Protocol) Server, getting time from an atomic clock.