AWOL and Desertion
The 30 Day Rule
Once a member goes absent, each of the military services enters the member's information into their DIP (Deserter Information Point). At that time, the services take certain actions, such as stopping the member's pay and allowances and contacting family members in an attempt to locate the absent member and convince them to return to their unit.
On the 30th day, the member is "dropped from the unit rolls," (meaning the unit can fill the empty slot with a new person), and administratively classified as a "deserter." At that point, the DIP-folks electronically enter the information into the "Wanted Persons File" in the FBI's National Crime Information Center (NCIC) computer.
That means the information is available to every law enforcement agency in the United States, and the member becomes a "wanted person," subject to arrest by any police officer. United States Code, Title 10, Section 808 states:
Any civil officer having authority to apprehend offenders under the laws of the United States or of a State, Commonwealth, possession, or the District of Columbia may summarily apprehend a deserter from the armed forces and deliver him into the custody of those forces.
The DIP center also sends the information to the Department of State, who then cancels any passports the member may have.
The military doesn't necessarily have to wait the full 30 days before administratively classifying an absent member as a deserter. If the facts and circumstances show that the member intends to remain away permanently (an example would be if they left a note saying they were never going to return), then the member can immediately be classified as such.
Also, if he/she has gone to or remains in a foreign country and, while in the foreign country, has requested, applied for, or accepted, any type of asylum or residence permit from that country, they are immediately reclassified as a deserter. Other factors, such as whether the member is awaiting disposition for other military crimes at the time of AWOL, or if the member escapes from military prison, can also result in immediate classification as a deserter.
The most significant factor about administrative classification as a deserter is the shift in "burden of proof." If a member, who has been absent for 30 days or less is tried by court-martial, the burden of proof that the member intended to remain away from military control rests on the prosecution. To support a guilty verdict for desertion (vice AWOL), the prosecution would have to prove (beyond a reasonable doubt), that the member intended to remain away from the military forever.
However, once the absentee has been administratively declared a deserter, the burden of proof shifts to the defense. The court is allowed to assume that the member intended to remain away permanently unless the defense can provide clear evidence that the member intended to return to military control.