It has been my experience that the judges make the final decision about who
is excused from jury duty.  Here in California any person who has sole
caretaking responsibilities for a preschool age child or a needy adult can be
excused by mail.  I put off jury duty for the past ten years using this
"excuse".

I just went through the jury duty process.  They were selecting juries for
many different cases including the Richard Allen Davis/Polly Klaas trial.  I
was concerned how to get out of my civic duty, especially if it meant a
sequestered jury!  Alas, I waited all day to be interviewed in a alleged
prostitution case involving police entrapment and five lap dancers from the
Kit Kat Klub. The questions posed to the prospective jurors were awful:  how
do you feel about legalized prostitution?  have you ever engaged in
prostitution?  do you know anyone who has?  do you watch x-rated movies?  do
you own any x-rated movies?  do you read any x-rated material?....   People
were excused for a variety of reasons.  A woman had a mother with cancer who
might take a turn for the worse and need her at any minute.  A
commission-only car salesman didn't want to miss the annual Blowout
SuperSALE.  A woman's five year old was having a Barney Birthday Party and
the invitations were already sent out.  A man scheduled a vacation for the
next week and wanted to repaint his house, not sit on a jury.  A pregnant
woman worried about her swollen ankles and if she could elevate them during
the trial.  All those people were excused with a thank you and were told they
had fulfilled their responsibility for the next three years.

I don't think a mother caring for a toddler, nursing or not, would be asked
to serve.

Elizabeth