They are sent by police and prosecutors who hope Collins and her 11 analysts at the National Center for Missing and Exploited Children can verify that the graphic pictures are real, not computer-generated. When they can't, officials sometimes turn to outside experts.

All this is being done — at an annual cost in the millions of dollars collectively in child-pornography cases alone — as software like Photoshop makes it easier to fake photos and as juries become more skeptical about what they see.

Although challenges to digital photos come in all types of criminal and civil cases, they are especially pronounced in child-pornography cases because of a 2002 U.S. Supreme Court decision striking down a ban on computer-generated child pornography. Defense attorneys are trying to use the ruling to introduce reasonable doubt in jurors' minds about the images' authenticity.

Prosecutors still generally prevail, but "this has certainly created an additional burden," said Thomas Kerle of the Massachusetts State Police. "I can say that unequivocally, it has made the prosecution of these types of cases more difficult. It takes ... resources I think could be better applied to investigating" more cases.

Drew Oosterbaan, who heads the U.S. Department of Justice's Child Exploitation and Obscenity Section, said prosecutors sometimes submit only photos they can easily verify because outside experts can be expensive — with travel, hotels and consulting fees, along with possible delays.

"This can affect the sentence the defendant gets," he said. "Before (the 2002 ruling) we would generally charge all the images."

Oosterbaan added that although defense lawyers have the right — and duty — to challenge evidence, they are doing so without "any shred of evidence there are wholly computer-generated images being generally circulated and passed off as real children out there."

And many law-enforcement officials worry that the time and money needed to withstand any challenges will only grow as technology improves and makes it more difficult to tell a computer-generated image from a real one.

"I feel that pretty much we can tell the difference right now," said Karl Youngblood of the Alabama Bureau of Investigation. "How much longer that's going to last, I don't know with the technology going at the rate it's going."

Of course, there's a cost to defendants as well — sometimes more so because federal law limits where and when the defense may review images to restrict their distribution, meaning experts must often travel with expensive equipment to a police lab in another city.

"If something becomes more difficult for the government to prove, so be it. They have the burden of proof," said First Amendment lawyer Louis Sirkin, lead counsel in the challenge that led to the 2002 Supreme Court ruling.

Child pornography is illegal in the United States, but the Supreme Court in 2002 struck down on free-speech grounds a 1996 federal ban on material that "appears to be" a child in a sexually explicit situation. That ruling covers computer-generated images, though morphing — such as the grafting of a child's school picture onto a naked body — remains illegal.

Collins' Child Victim Identification Program in Alexandria, Va., grew out of that ruling. After officials submit seized photos, the center uses software and visual inspections to look for matches. It can usually verify that children in some or all of the images are known and real.

The program, which costs about $1 million a year to run, now has about 1,300 children in its database, up from 20 in 2002. Staff grew from just Collins then to 11 full-time analysts who now work under her. The program reviewed 5 million images last year, up from about 450,000 in 2003, the program's first full year.

Because of the graphic nature of the images, a psychologist visits each week, and analysts must undergo counseling at least quarterly.

"Not everybody can do it," said Raymond Smith, a longtime investigator who oversees child-exploitation cases at the U.S. Postal Inspection Service. "You have to be able to come to grips with seeing children be victimized and abused. It can tear you up, (but) through your efforts you are identifying the people that hurt these children."

When the center cannot make a match, prosecutors can turn to outside experts. Sometimes, it's a pediatrician who can say a real child has characteristics matching those seen in the photo. Other times it's a computer expert who can talk about how difficult it is to produce images and video of that quality.

Hany Farid, a Dartmouth College professor who has testified for the prosecution in some cases, said he has been getting more inquiries about authenticity — not only for child-pornography cases but also civil lawsuits questioning medical images in malpractice cases or signatures in contract disputes. News organizations have also looking for ways to authenticate photos.

"Because so many people get photographic fakes in their (electronic) mailboxes, to the average juror it resonates," he said.

The challenges can be costly, even if a case never goes to trial — the majority end in plea agreements.

Farid said he charges up to $25,000 a year for software he produced to look for signs of tampering, such as inconsistencies in shadows. He also charges as much as tens of thousands of dollars to work on a case.

Even when there is a match and an expert isn't needed, a prosecutor must seek out the detective who initially identified a child for the center. That detective must often be flown in and be ready to testify if the defense raises a challenge. In one case in Portland, Maine, a Russian detective couldn't be reached, so the prosecutor had to spend $5,000 on an expert anyway. Trials get postponed if a key witness has a scheduling conflict.

Sam Guiberson, a defense attorney who specializes in technology and digital evidence, said challenges to evidence are to be expected, digital or not.

"Every good trial lawyer is always going to subject every part of his adversary's exhibits to that sort of scrutiny," Guiberson said.

Kebin Haller, deputy director of the Wyoming Division of Criminal Investigation, said that in most cases, a large quantity of images are seized such that enough hold up.

How much proof a prosecutor needs in child-pornography cases can vary from region to region and even from judge to judge. Recent federal appellate rulings have eased the burden on prosecutors, essentially saying that in lieu of definitive evidence, they can let jurors make up their own minds about whether an image is real or computer-generated.

Many prosecutors, though, don't want to take that chance and would rather submit proof.

"It's difficult to prove these are real children," said Mary Leary, a Catholic University law professor who previously worked on child-abuse and child-pornography cases. "Is the defense exploiting this? Absolutely they are."

We called around to firms to find out whether associate salaries, called economically-irrational in some quarters, have finally (or, at least, for now) hit a ceiling. The answer seems to be yes.

“We’re not going to do anything,” said Orrick spokeman Allan Whitescarver, noting that law firms compete for talent with investment banks and consulting firms. “Times aren’t good for them either,” said Whitescarver. “We’re going to sit tight and keep the salaries capped.”

We’d venture to guess, however, that few big firm chairmen wake up on Jan. 1 and say, “you know what, our associates don’t make enough money; let’s bump their salaries!” What typically happens is that a single firm, in an attempt to flex its muscles, raises salaries, and everyone else follows, fearing the fallout if they don’t. Simpson Thacher was the eager beaver last year.

Whitescarver leaves room for this possibility. “If other firms move up, we and others will follow.”

Other firms, including WilmerHale and Milbank, also told the Law Blog that, for now, first-year salaries will stay at $160,000.

Recently, on the American version of the TV show “The Office,” two of the main characters — Jim and Pam — confess to their co-workers that they’ve become romantically involved. In the spirit of openness and responsibility, the couple goes to the head of human resources, Toby, to ask whether they need to sign something attesting to their relationship. Toby (Paul Lieberstein), who also has a thing for Pam, tells them that won’t be necessary.

With Valentines Day upon us, we found ourselves asking: What would’ve happened if Jim and Pam were lawyers? Would they have insisted on signing a love contract to establish their rights and remedies in the event of a break-up? If Jim and Pam were both hard-working associates, would their relationship be more susceptible to trouble?

To work through these relationship issues — and the law that governs them — we caught up with Ashley Brightwell, a partner at Alston & Bird in Atlanta. Brightwell, who focuses on employment litigation, filled us in on the rise of love contracts, the phenomenon of lawyers who date lawyers and best practices for conducting a firm romance.

Hi Ashley. Thanks for chatting. So you’re a specialist on office romances. Talk about that a bit.

I do a lot of sexual harassment cases, mostly defending the company. Of sex harassment cases, I’d say a third stem from something that arguably began as a consensual relationship – either formal dating, or an affair — and then morphs into a bad break-up or something that’s no longer consensual. Or, just something as simple as inter-office flirtation where one party thought it was mutual, and the other party either never thought it was, or things progressed into it becoming unwelcome.

What are “love contracts”?

It used to be that many companies had strict prohibitions on office romances. Then they recognized that wasn’t going to work, and that no matter what the policies were, employees were going to get involved. That’s when the idea of a love contract came along. It’s a tool that employers use to protect themselves when an office romance goes sour. It’s a document that confirms that a relationship is voluntary and informs the parties of the company’s sexual harassment policies. It sets out a procedure if, at any point, the relationship goes south.

Let’s focus on law firms. We’ve heard a lot about the concept of “firm boyfriends” and “firm girlfriends.” Not romances, but the kinds of close relationships that develop between lawyers who spend more time with each other than they do with their families. Do a lot of law firm affairs begin like that?

I don’t have hard stats to back this up, but the number of affairs in law firms and romances that end up in marriage seem to be greater than in the general population. In large part, it’s because you’ve got a lot of people who are close in age, doing the same work, working alongside each other and putting in long hours. It’s inevitable, in those circumstances, that you’re going to have a lot of office romances.

What are the major pitfalls for lawyers who date lawyers? Take a partner dating an associate, for example.

I think when you’ve got a partner and an associate you’ve got two big issues. First is the fact that a partner can control the associate. Whether the relationship is going great or whether it goes south, the partner can really affect the person’s employment – in terms of the work they get, their reviews, and possibly even their salaries. The other issue is this: the perception among other associates and partners. For instance, if a female associate is getting great benefits because of a relationship it can result in hostile work environment claims from those outside the relationship.

Let’s try a hypothetical. I’m a sleep-deprived second-year associate who can’t find much time to socialize outside of work. One day I come running into your office, jump up and down on your couch, and confess that — on a firm-sponsored booze cruise — I fell in love with a summer associate. Advise me.

First you look and see what your firm’s policies say. If relationships are permissible in your organization, then there shouldn’t be a problem as far as HR or management are concerned. But I’d still advise informing someone higher up that it’s going on. And if that summer decides to become a lawyer at your firm, I’d take whatever steps I could to make sure you’re not working with that person. I’d avoid day-to-day interaction.

But I don’t need to fight my feelings, right?

Well, firms and companies are recognizing that if you have a policy against office romances, it’s just going to be broken. So they’re dealing with them in different ways – whether you call it a love contract or something less cheesy. So often I see things go bad, and then one person comes in and says it was never consensual to begin with. Typically, that person can produce a big stack of emails which look quite bad. But you can prevent a lot with a love contract in which the parties agree it’s voluntary.

The New York Observer has answered a burning political question that never occurred to us, at least until now: "If the major presidential candidates were top New York law firms, which ones would they be?"

Lawyers in New York - perhaps enjoying a bit more idle time than usual these days - energetically took up the question, offering all kinds of suggestions and nominations, David Lat wrote. Lawyers nationwide have showered Hillary Clinton with more campaign contributions than any other candidate, federal records show. In Mr. Lat's informal survey, though, when asked which firm most embodies Mrs. Clinton, the common answer from lawyers in her home state was "Not mine."

So how did the pairings shape up?

After some debate, Mr. Lat declared Paul, Weiss, Rifkind, Wharton & Garrison the closest match for Mrs. Clinton. Why Paul Weiss? One anonymous lawyer at the firm suggested that, like the candidate, the firm had a reputation for being a bit, well, hard-driving. (The lawyer actually used a more colorful phrase.) "But those who know her - and us - know we are 'good people,'" the lawyer added.

Another lawyer nominated Wachtell, Lipton, Rosen & Katz, the boutique firm known for advising in big mergers and defending chief executives under siege, as a match for Mrs. Clinton, suggesting they both had a "thorough command of the issues." This caused a Wachtell associate to snort back, "Can you picture Wachtell crying?"

Many lawyers pitched their employers as the Barack Obama of law firms, but Mr. Lat gave that title to Quinn Emanuel Urquhart Oliver & Hedges, a relatively young business-litigation firm where, according to a recent article in The New York Times, "flip-flops are acceptable footwear."

"Both seem to be the young, upstart contenders, trying to do things a new way," was how one observer put it.

On the Republican side, John McCain got paired with Cravath, Swaine & Moore, but only after plenty of jokes about being old - and at least one reference to torture.

Finding a match for Mitt Romney was apparently a cinch: It was Sullivan & Cromwell, a law firm that consistently ranks near the top of the merger advisory league tables. A former associate at the firm offered these common traits: "Very picture-perfect. Always willing to go with the highest bidder."

The Supreme Court's long-running debate over the meaning of federalism took a new turn in a case the justices heard on Monday.

The question was, What happens when a state chooses to give criminal suspects more protection than the federal Constitution requires? If an arrest is improper under state law, does that mean that a search the police conduct in connection with the arrest is necessarily improper as well, even if the arrest met constitutional standards?

It is a question that has divided courts around the country, since it is not unusual for states to offer more vigorous protection for individual rights, either by their own constitutions or by statute, than that provided by the federal Constitution, as interpreted by the Supreme Court.

In this case, the police in Virginia arrested a man for driving with a suspended license. Under Virginia law, that offense is a misdemeanor that does not justify an arrest, except in unusual circumstances. Ordinarily, the police are limited to issuing a summons and a notice to appear in court.

Nonetheless, the police took the man, David L. Moore, into custody and in the search that followed found 16 grams of crack cocaine (about a half ounce) and $516 in cash. Mr. Moore was convicted of the drug offense and sentenced to five years in prison. The Virginia Supreme Court dismissed all charges, ruling that because the arrest was unlawful, so was the search.

Under the United States Supreme Court's precedents, searches that are "incident to a lawful arrest" are considered valid. During the argument on Monday, there was general agreement that the arrest itself was supported by probable cause, the standard under the Fourth Amendment of the Constitution. But given the state law, could the arrest be considered "lawful"?

Arguing for Virginia, which was appealing a decision by its state Supreme Court, Stephen B. McCullough said that "there was a violation of state law, but it wasn't a constitutional problem."

Mr. McCullough, a deputy state solicitor general, told the justices: "You have clear rules. Why would you trade them in for a morass? An arrest is constitutional if the officers have probable cause to believe a crime has been committed."

The rules were actually not quite so clear. Michael R. Dreeben, a deputy United States solicitor general who argued for the Justice Department in support of Virginia, told the justices that "admittedly, I think neither side is able to point to a case that squarely addressed and conclusively resolved the issue that's before the court."

Nonetheless, Mr. Dreeben maintained that it would be counterproductive to declare a search to be unconstitutional under these circumstances. "It's clear that imposing such a Fourth Amendment rule would do nothing other than discourage the states from providing additional restrictions as a matter of their own state's law that may serve to protect citizen privacy interests above the floor that this court has identified as required," he said.

Thomas C. Goldstein, arguing for the defendant, told the justices that under English common law, an illegal arrest was considered a form of trespass. "Because at common law you could not search someone pursuant to an arrest that was a trespass," he said, "the search itself is unconstitutional."

Chief Justice John G. Roberts Jr. was not persuaded. "It's not a lawful arrest," he said. "But that's a different question than whether or not it is an arrest. Our precedents say if it's an arrest, you can search ‘incident to the arrest.' "

"I disagree," Mr. Goldstein said. The court's precedents, he continued, indicated "that it has to be an arrest that is lawful under state law." The case came down to a simple concept that would be easy to administer, Mr. Goldstein said: "A rule that simply says to the police officer, ‘If you're allowed to arrest him, arrest him; if you're not, you're not, and you can't search him constitutionally.' "

Several justices pressed Mr. McCullough, Virginia's lawyer, on where, given a variety of dubious arrests, he would draw the line between valid and invalid searches. Justice Antonin Scalia asked whether, as a Supreme Court justice, he could search a neighbor's house on suspicion that marijuana was being grown there.

Yes, if the justice, as a federal employee acting on behalf of the government, had probable cause, Mr. McCullough said.

How about a "federally employed janitor?" Justice Scalia asked. "His neighbor is growing marijuana, and he's just as offended as a Supreme Court justice would be. Can he conduct a search?"

The lawyer replied, "I think if he's doing it on behalf of the state, the answer is yes."

Justice Scalia said, "Wow."

The case is Virginia v. Moore, No. 06-1082.