Is random jury selection necessary to ensure defendants receive a fair trial?

In your 15 May 2011 podcast, you discussed whether or not it is moral to compel people to serve on juries. I agree with your conclusion that it is not moral, and that jury duty should instead be voluntary. But you went on to suggest that volunteers should be able to choose what time range to serve, and even what case to serve on. Wouldn't this just lead to attempts to 'stack' juries? An influential organization could encourage, and perhaps even compensate, its members to 'volunteer' for a certain case, thereby influencing the outcome. For example, an anti-abortion organization could try to 'stack' the jury for the trial of an abortion doctor. Of course the pro-choice organizations could try and counter with the same, but that just means the verdict is ultimately determined not by objectivity, but by numbers -- by whoever is able to round up more volunteers. Isn't a random selection process necessary to keep this sort of influence out of the system and thereby ensure that defendants receive a fair and impartial trial?