The Justice Department just approved New York's right to count prisoners in their home districts, rather than in their county of incarceration. How will that change the state legislative map in a year when redistricting reform already has blood boiling in Albany?

Until now, the practice in New York has been to count the prisoners incarcerated in a county as residents of that county, even if that's not where they previously lived or voted. That's pursuant to the U.S. Census' "usual residence" rule, which holds that "counting prisoners at a 'permanent home of record' address, rather than at their place of incarceration, would result in increased cost to the federal, state, and local correctional facilities that would be required to participate in data collection efforts."

As a result, regions with more correctional facilities get a bump in their headcount, even though the people being counted a) aren't exactly "residents," and b) can't vote.

Critics say that unfairly inflates the electoral impact of certain localities: in New York, the Citizens Redistricting Committee argues that "half of a Rome City Council ward is incarcerated, giving the residents of that ward twice the influence of other city residents"; the Prison Policy Initiative claims that seven State Senate districts in upstate New York only meet the minimum population requirements because of their prisons.

According to New York Department of Correctional Services statistics released last July, of the prison system's 56,989 inmates and work-release prisoners, 34,308 come from New York City and surrounding suburbs downstate. That's 60 percent of the state's incarcerated. Only nine prison facilities out of 71 are located in these same counties, and they're mostly small minimum security joints.

Prisoners get sent upstate, then they get counted there. Imagine a straw sucking people from Democratic districts and using them to pad Republican ones. That's the effect of the state prison system when it comes time to redistrict.

According to the Citizens Redistricting Committee and the Prison Policy Initiative, counting prisoners in their original place of residence could result in more Democrat-leaning districts and fewer Republican ones. No surprise, then, that Republican State Senators are challenging a 2010 law that would require New York to review every single inmate's home address and reapportion the federal census count appropriately.

Passed last summer, Section 57, Part XX of New York state law requires that in each year that a federal decennial census is conducted, but does not take into account an incarcerated person's home address, the Department of Correctional Services must provide that information to the legislature so that they may draw State Assembly and Senate districts accordingly. The state would still have to abide by the Census' counting methods when redrawing congressional districts at the federal level.

Senator Elizabeth Little and eight other Republican State Senators (all from districts with large prison populations) have filed a lawsuit against Part XX. They argue the following:

1) that the law was passed as part of a revenue bill, but it has nothing to do with revenue and should not have been allowed;

2) that although Article II, Section 4 of the state constitution reads, "For the purpose of voting, no person shall be deemed to have gained or lost a residence, by reason of his or her presence or absence...while confined in any public prison," inmates can't vote, and so they gain or lose nothing by being counted at the institution of confinement;

3) that the federal census, which counts inmates at their place of incarceration, uses in its estimations sound enough logic so as to preclude a state doing it any other way; and

4) that prisoners draw upon the services of the community in which they're incarcerated; that they are without other legal residence and thus impossible to count as "from" anywhere else; and that death sentences or those of indeterminate length mean certain prisoners will never return to the their prior homes.

Even if Part XX was passed illegitimately, per the first argument, the law makes a change that appears to be already in the state constitution. Hence the second argument, which is probably what this case will boil down to: what's meant by, "For the purpose of voting"?

Little's lawsuit interprets the "purpose of voting" to be divorced from the "purpose of enumeration," but that raises more questions. Why say prisoners don't gain or lose a residence while incarcerated, when it's already illegal for them to vote? That seems to suggest that the "purpose of voting" encompassed more than an individual's right to participate in an election. Rather, the "purpose of voting" might take into account not just the act itself, but also certain processes that might affect the the value of a vote—like, say, redistricting.

An incarcerated person can't vote, but their incarceration in a different community may dilute votes from their home district. That has a disproportionate effect on voters of color, says Erika Wood, Director of the Brennan Center's Redistricting Project. Her organization, along with several other voting rights groups, recently filed a motion asking to intervene to help defend the Part XX against the lawsuit.

"[The old method] has really decimated the voting strengths of poor and minority communities," Wood said. "By allocating people in prison to the districts where they're incarcerated, it artificially inflates the size of those prison districts, but at the same time dilutes the voting strength of every other district that doesnt have a prison in it."

Should the strength of your vote suffer your neighbor's crime? Perhaps that's what the state constitution meant to guard against.

But standing practice is as fraught as the alternative. Republicans contend that counting prisoners in their former homes is irrational, as it relies on unfounded assumptions and corrects one distortion with another. "Why should a lifer, who will never be returning to their community of original incarceration, be counted in that community, when in fact they will be living in a prison the rest of their life?" asked Republican State Senator John Bonacic. "How do you count a transient prisoner whose family no longer resides in their community of incarceration as living in that community? It is unreasonable.

"The only inmates who potentially should be considered," Bonacic said, "are those serving shorter sentences who have a clear and existing community connection at the time of the census, and who have a reasonable probability of returning to that residence." Perhaps inmates who just happened to be doing a stint during a census year may be counted in their hometowns?

The case hinges ultimately upon two things: whether one method of counting is more distorting or unfair than another—downstate already counts a lot of ineligible voters—and to what degree the state's redistricting process should defer to federal Census standards.

"There's no reason why a state can't decide how they want to allocate people in prison and try to do something a little bit fairer and more just," said Erika Wood. The U.S. Census won't argue with her. Despite the "usual residence" rule, a bureau representative characterized the Census' methods as a "base" upon which states can make their own counting decisions when determining state legislative districts. They also point out that Kansas and Hawaii require population figures to reflect the home addresses of military personnel, rather than the place at which they're stationed. The U.S. Census doesn't.

Without objection from the Census or the Department of Justice, the Republican lawsuit will go to the State Supreme Court unaided. Attorney General Eric Schneiderman will defend the law, which he co-sponsored while a State Senator last year.