The great criminal defense blog, Simple Justice, has an excellent post about juries and their ability to follow jury instructions. The case cited occurred in Stamford, Connecticut in which a jury returned a verdict of Guilty in a manslaughter case and when polled by the Judge changed their verdict to Not Guilty. It had become apparent to the trial Judge that the jury had misunderstood the jury instructions and they had intended to find the defendant Not Guilty with their original verdict.
Lawyers put a lot of thought into jury instructions and in Texas an error in the Jury instructions makes an excellent ground for appeal. I have often wondered if the jury instructions can really be understood by jurors. Most judges take their jury instructions from old court charges they have used for years. The language is full of old legal verbiage and can’t be understood by most lawyers. let alone your average juror.
I believe in most cases jurors know what verdict they want to find and ignore the jury instructions that stand in their way. I have also seen cases where jurors will use their own interpretation of the instructions to convince other jurors to vote their way and justify the verdict they want.