I'm not sure if this is still relevant, but... I was just looking at Casey's cell phone records (e.g., at
http://www.docstoc.com/docs/1626040/Casey-Phone-Log-Page-51_75 ) and they include the IMEI and the IMSI. The IMEI is like a unique serial number for a cell phone, and the IMSI is like a unique serial number for a sim card. The records I linked to always show the same IMEI and IMSI. But, if she was switching her sim to a different phone for any of the phone calls or SMS's, we would see
the same IMSI but
a different IMEI for those calls. The odd thing is that there are some spots with a
missing IMEI. Those spots also have missing entries for the cell tower IDs, but the towers had to be contacted, so it seems like some kind of glitch in the recording. I wonder what the deal is with these. (I know LE was talking about how there were missing or conflicting entries between the ATT records and the Billing records; maybe these are what they refer to?)
If the records really do show the same IMEI and IMSI for all the calls/SMS's, then Casey could have had another phone with a different sim card (and thus a different phone number), but she sent text messages and made calls and was IMming etc. on the computer so frequently that it's tough to see how she could have fit in more usage than what we already know about. Also, none of the other phones (like her friends' phones) that LE checked show a different # for Casey, to my knowledge. Maybe the other phone+sim&number was exclusively for contact with Zanny