If a key witness to a murder has a history of drug-abuse, will his credibilty be questioned in court?

If a key witness to a murder has an extensive background of drug-abuse, will jurors believe him/her? Will his “credibility be questioned? Is it possible to screen a key witness’s background before testifying in court? Please Help.

More Meth Drug Addiction Info:

• Jodie Sweetin Talks Drug Abuse
• Suboxone Fast Passing Methadone As Preferred Method Of Treatment …
• Iman: Part 2 « Umm Ibraheem
• Move to Strike My Last Post! « North Carolina Criminal Law
• drug abuse rehabilitation » Blog Archive » Drug Abuse Rehab that …
• Return of Ghost of Altantuya: Bala still waiting to meet MACC …
• Turkey – Key testimony from secret witness at 13th hearing in …
• Tea Time » Understanding The Drug Abuse Alcohol
• PI Newswire :: Jurors May Be Swayed by a Pretty Face, Study Finds
• » New National Drug Abuse Strategy Emphasizes Prevention …