Smith attended Blair High School in Pasadena, California, where he played football, basketball, and ran track.

In football, he gained All-Conference, All-State, and All-American honors as a senior after rushing for over 1,500 yards with 18 touchdowns, helping lead Blair High School to its best record in 10 years.

He had four interceptions, which was the best for a single player in the Mountain West that year, and tied the Utah single-game record with four pass breakups against the New Mexico Lobos toward the end of the 2007 season.

Smith's best performance, though, may have come in the 2009 Sugar Bowl, where he had six tackles, a sack, a forced fumble and a huge pass breakup in Utah's stunning 31-17 victory over the Alabama Crimson Tide.

[3] Smith entered the 2009 NFL Draft as a highly touted cornerback prospect that possessed one of the biggest frames ever seen for the position.

[7] Throughout training camp, Smith competed to be a starting cornerback against veterans Jason Allen, Eric Green, and rookie first round pick Vontae Davis.

[9] He made his professional regular season debut in the Miami Dolphins' season-high-opener at the Atlanta Falcons and recorded two solo tackles and deflected two passes in their 19–7 loss.

On September 6, 2010, head coach Tony Sparano surprised many analysts and fans when he announced Jason Allen would replace Sean Smith as the starting cornerback for the season-opener.

[14] He was demoted after struggling against wide receivers Roddy White and Sam Hurd during the preseason and was a healthy scratch for the Dolphins' 15–10 victory at the Buffalo Bills in the season-opener.

On October 31, 2010, Smith recorded a tackle, deflected two passes, and made his first career interception in the Dolphins' 22–14 victory at the Cincinnati Bengals in Week 8.

He intercepted a pass attempt by quarterback Carson Palmer, that was intended for wide receiver Terrell Owens, and returned it for an 18-yard gain before being tackled by Andre Caldwell.

[15] His performance earned him back his job as a starting cornerback as he replaced Jason Allen who was subsequently waived on November 10, 2010.

[25] As a top free agent, he received interest from multiple teams, including the Kansas City Chiefs, Philadelphia Eagles, Tampa Bay Buccaneers, New England Patriots, and the Arizona Cardinals.

[30] Head coach Andy Reid named Smith a starting cornerback to begin the regular season, opposite Brandon Flowers.

[32] On November 3, 2013, he made two combined tackles, two pass deflections, an interception, and scored his first career touchdown in the Chiefs' 23–13 win at the Buffalo Bills in Week 9.

[35] On September 29, 2014, Smith made a season-high two pass deflections, three solo tackles, and an interception during a 41–14 victory against the New England Patriots in Week 4.

[37] On July 24, 2015, the NFL announced that Smith would be suspended for the first three games of the 2015 season after pleading guilty to a DUI charge earlier in April.

[29] Head coach Jack Del Rio named Smith and David Amerson the starting cornerback duo to begin the 2016 season.

[52] Head coach Jack Del Rio benched him in favor of rookie Gareon Conley after a poor performance against the Baltimore Ravens in Week 5.

[61] Smith pleaded guilty to the DUI charge on April 15, 2015, and was sentenced to two years of probation, as well as, fined $895 after failing to present proof of insurance.

Smith allegedly beat then stomped on a male victim's head near the corner of Arroyo Parkway and Colorado Boulevard early in the morning on July 4, 2017.

Woods claimed he suffered from hematomas to the left and right side of his head, and required a metal plate and screws to repair facial fractures.