First peel the peaches. Cut an X at the bottom then lower them into a pot of boiling water for about 20 seconds. Using a slotted spoon, transfer them to a collander and shock them with cold water. Let them cool and the skin will peel right off.
Cut the peaches in half, remove the pits and cut them into chunks. Cook them with the water in a medium, nonreactive saucepan over medium heat, covered, stirring once or twice, until soft and cooked through, about 10 minutes.
Remove from heat, stir in the sugar and then cool to room temperature. Remove about 1/4 of the peaches and cut them into slightly smaller chunks and reserve. Puree the rest of the peaches and their liquid in a blender or food processor with the sour cream, heavy cream, vanilla and lemon juice until almost smooth. Add the reserved peaches back in and chill the mixture thoroughly, preferably overnight, in the refrigerator.
Freeze in your ice cream maker according to directions.
An hour or so before churning the ice cream, make the raspberry swirl by mashing the raspberries together with the sugar and vodka with a fork until they're juice but with nice-sized chunks of raspberry remaining. Chill until ready to use.
When you remove the peach ice cream from the ice cream machine, layer it in a container with spoonfuls of the chilled raspberry-swirl mixture. Freeze until ready to serve. It will get really hard after about 3 hours, so you may want to let it warm up a little for ease of scooping. Garnish with fresh raspberries.