Sometimes a comma helps:
Saw this sentence today on an e-mail alert I get from a newspaper. A lack of forensic evidence, the easy access to ricin, a nation full of people who have axes to grind and no apparent eyewitnesses add up to making the case hard to solve, experts told xxxxxxxxxx.
It's fine, except for one weakness -- an additonal comma would have helped. We malign this little mark, and it is often oversued. But this little speed bump has a place. Above, for instance, it could promote a bit of clarity and prevent a bit of momentary confusion. As written, a reader might briefly trip over the last two items of that series. Is the writer saying there is a nation full of people who have no axes to grind and who (have) no eyewitnesses (that verb wants to jump the gap)? No, I don't think so. So putting in the comma makes it clear that "no apparent eyewitnesses" is a separate element:
A lack of forensic evidence, the easy access to ricin, a nation full of people who have axes to grind, and no apparent eyewitnesses add up to making the case hard to solve, experts told xxxxxxx.