A 10-year NFL veteran and two-time Pro Bowl cornerback with the San Diego Chargers, Byrd spent the last three years as an assistant with the St. Louis Rams. He was the defensive assistant from 2003-04 and the assistant secondary coach in 2005. He worked with Smith, who was the defensive coordinator in St. Louis from 2001-03, in his first season with the Rams.
"Coach Smith is a great teacher and a great person," Byrd said on the team website. "I like his philosophy and his attitude. He obviously played a big role in me being here and I'm grateful to the Bears organization for this opportunity."
From 1999-2001 he was the executive director/player programs and community affairs with the Green Bay Packers.
Drafted in the first round, 22nd overall, by the Chargers out of San Diego State in the 1983 NFL Draft, Byrd retired after the 1991 season as the third-leading interceptor in the NFL with 42.
The Bears also promoted Lloyd Lee to defensive assistant. He spent two seasons as Chicago's defensive quality control coach after serving three seasons as a pro scout with the Tampa Bay Buccaneers.
Lee had been a candidate to become the linebackers coach with the Buffalo Bills, but will now assist with the nickel package and linebackers in Chicago.
WR Mark Bradley, who suffered a torn ACL on Oct. 30, has begun his rehabilitation and is expected back on the field sometime in June. That would mean he'll likely miss mini-camp in May, but could do some light work during organized team activities.
If the current timeframe holds true, Bradley should be ready to practice when the team opens training camp, which is expected to be sometime in late July.
However, there are no guarantees coming off knee surgery and the team is likely to address wideout either through free agency or the draft.
Bradley averaged 12.8 yards on 18 receptions before going down in his best game as a rookie. In the first half against the Detroit Lions, he caught 5 balls for 88 yards, including a 54-yard gain.
Despite playing in only seven games with four starts, Bradley finished fifth on the team in catches and fourth with 230 yards receiving.