He played college football for the Arizona State Sun Devils and was selected by the Oakland Raiders in the third round of the 2005 NFL draft.

Prior to his NFL career, Walter played quarterback for his hometown school, Arizona State University (ASU) where he earned a BA in communication.

He also set numerous school records, which include most passing yards (10,616), most completions (777), most touchdowns (85), and total offense (10,142).

After a 4–7 record under new head coach Dirk Koetter and only one win in the Pacific-10 Conference, Krohn transferred out of ASU following the season.

This turned out not to be the case, however, when Walter was kept as the backup after redshirt freshman, Chad Christiansen, had impressive spring and fall practices.

The injury did not prove to be a factor as Walter connected with wide receiver Shaun McDonald for a 72-yard touchdown pass on his first play from scrimmage.

After falling behind 21–0 in the second quarter, Walter led the Sun Devils to a 45–42 upset win over the Ducks, breaking a Pac-10 single game record for passing with 536 yards.

ASU ended the regular season with an 8–5 record and nearly upset the Kansas State Wildcats, who were favored by 17 points over the Devils, in the 2002 Holiday Bowl.

Despite the Sun Devils achieving a 5–7 record (2–6 in the Pac-10), Walter still threw for 3,044 yards, including the game-winning touchdown against North Carolina as time expired.

Walter also earned the Territorial Cup MVP when ASU beat their arch-rivals the University of Arizona at Sun Devil Stadium.

Walter played in only two preseason games because of a groin injury, one that eventually required surgery at the conclusion of the 2005 season.

Entering the 2006 season, Walter was expected to compete for the starting quarterback position with Tuiasosopo and Aaron Brooks.

[citation needed] Walter lost in the 2014 Republican primary election against Wendy Rogers for the House of Representatives seat in Arizona's 9th congressional district.